Having previously worked in an bookstore as well as an archives and studied history most of my life; it depends on what you want to get out of it. If youre looking for something scholarly, unbiased (as unbiased as you can reasonably get) and overarching, there are a lot of good books geared towards that:

Cambridge History of Scandinavia - Knut Helle

Europe: A History - Norman Davies

Cambridge History of Islam - Bernard Lewis (some will question this ones objectivity)

What you want to take away from searching for something scholarly is its purpose. Is the title loaded (i.e. Amsterdam: A History of the Most Liberal City - Russell Shorto. While this is a fantastic book, it seeks only to prove that Amsterdam is Liberal so I question its objectives as a straightforward history as the author likely omits that which makes Amsterdam non-liberal). Another question you should ask is who published the book. A surprising amount of people overlook this. Scholarly and University presses are usually the best in terms of legitimacy in the history field, while other publishers like RandomHouse or Penguin Classics can and do produce legitimate writings but they are a business who need to make money through sales; therefore they offer a product that will be consumed which usually in turn means top-down history.

This all being said, there are hundreds of fantastic and legitimate history books out there that are written not like the tomes I listed above, but rather to entertain the reader. These are usually much more focused in their history; something many historians call "micro-history" which focuses on a very specific place in time, or person (as oppose to macro-history which focuses on, say, a country). Some examples that I always recommend to those who are recently interested in history:

The Lost City of Z - David Grann

• Focuses on Percy Fawcett, an early 20th century explorer of the Amazon, considered one of the final true explorers. He may also have possibly been an inspiration for Indiana Jones' fictional character.

Devil in the White City - Erik Larsson

• Focuses on the Chicago 1893 World Fair, the troubles they had building it and its cultural significance as well as the story of H.H. Holmes, one of the United States first recorded serial murders who took advantage of visitors of the world fair.

The War that Ended Peace - Margaret MacMillan

• Focuses largely on the political, cultural and human impact leading up to the outbreak of the First World War.

Columbus: The Four Voyages - Laurence Bergreen

• Focuses on Columbus as an individual and the impact his voyages had upon the world at that time.

Each one of these has a particular aim which can be very specific. Erik Larssons book which is one of my all time favourite history books but spans only a few years and deals with only around 10 major players. You will walk away with an idea of the cultural state in the United States and their relation with the world; but its not an in depth study of the United States as a rising power. The third and last type of books I point out to people are the targeted general history books. That is to say, ones with a broader scope, but not so much that you have no contextual references and they just throw facts at you. The best books thus far I have come across like this:

Rubicon - Tom Holland

• Gives a fairly concise history of the rise and fall of the Roman Republic from the Gracchi to Augustus.

A History of the Habsburg Empire - Robert Kann

• One of the few books that deals with both Spanish and Austrain-Hungarian Habsburgs through their entire duration.

Lords of the Horizon: History of the Ottoman Empire - Jason Goodman

• Details the rise and fall of the Ottomans; I am disinclined to agree with his central hypothesis but he defiantly covers his bases in terms of history

tl;dr - Depends what you want: Scholarly Overview - Check who the publisher is and why they published it Entertainment - Be wary of taking everything for truth, but are easy good reads Middle-of-the-Road - it may speak in general terms but will give you a good idea of the history.

If you want to take out Bad History Insurance, don't just read one book on a subject. Read two, or more!

It's pretty easy for one particular book to be bad history. You already know this. But how do you know which book at the store is crap, and which one is good? Well, the other answers here have made some great suggestions. Check the publisher, look for reviews, look up the author online, etc.

But the real way to be sure that you're getting the most out of your subject is to read more than one book on the same topic. You mention WWII as an interest elsewhere in the thread, so snag Beevor's book on D-Day. It is excellent. You get a good overview of the entire campaign. Then read Hans von Luck's book. He has a much more intimate view of the same campaign, as he was a commander during the battle on the German side. This is the point where you want to really read critically. Ask yourself a bunch of questions. Is there any difference between the two narratives? If Luck is saying something different, why is he doing so? What does he have to gain? What about his background would make him view things differently than Beevor?

When you're done with that second book, you're open to do whatever you would like. If you're burnt out on the subject, maybe grab a book on the Gallipoli campaign to see a different amphibious invasion with a very different outcome. Maybe switch to something completely different and expand your knowledge in another direction. But if the subject tickles your fancy, go back and read a third book. Maybe Pegasus Bridge, another intimate account of a small part of the D-Day battle. If you did so, you would have a lot of background to be able to judge the author (Stephen Ambrose) and his subjects.

So, I would encourage you to pick a subject that you know interests you. With WWI, WWII, and the French Revolution as your targets, you have more books to choose from than you could read in a lifetime. Grab more than one book on a subject and you reduce the danger of being seduced down a rabbit hole by one author. If you pick two authors that disagree on a subject, even better! Now you can take a side in the discussion and dive into the debate.

If you want specific book recommendations on a topic, you can ask here. You can also look for a flaired user that covers an area of interest for you and send them a PM. Many of us love to help folks out with book recommendations, and you'd have even more insurance against picking up a rubbish history book.

And just keep reading. Read topics here that you think are interesting. Read just about anything and you'll build up a store of knowledge and perspective that will help steer you away from the bad and toward the good.

As I'm not a professional, I can't answer your question as well as many here can, but I can tell you not to be too afraid to possibly accidentally read about a theory in some popular history book that is actually discredited by the scholarly community. You can easily read a more scholarly source on the topic and "unlearn" the discredited theory/version of events. Honestly, this might even be a good thing as you get to fully see the incorrect or now unpopular viewpoint of an argument and figure out for yourself why it is or is not the better view.

I'd recommend starting out reading the pop history books, such as Anthony Everitt or Adrian Goldsworthy's works, (along with the ancient historians and such, since they too are quite often proved to be most likely incorrect by modern scholars basing their facts on archaeology and such) and then getting into the more detailed and argumentative works such as Nathan Rosenstein or Ronald Syme. All these names are Ancient Roman examples, since that is my own field of self-study, but I'm sure if you told us your specific interests someone else here can you give you better recommendations.

I've learned so much from r/askhistorians. If you're interested in history you'd have a hard time finding a better source than suscriping and browsing the archives. If you're uncertain about something submit a question, the experts here are amazing.

On a slightly more practical note: I'm a big fan of reading history books on a tablet and frequently using wikipedia or google to look up places/people/events to reinforce what I'm reading.

Any introductory text is going to oversimplify, in a way that's their job. Here's my way of getting up to speed on a new topic.

1. Skim Wikipedia the broad topic.
2. Find a lecture or documentary on YouTube and take some notes about the Proper Nouns involved and get a general sense of the chronology. See if there's an opencourseware class on that specific topic or at least a single lecture.
3. Look up a class syllabus and see what their recommended reading is, see which scholars get cited the most, and see who argues against them. At this point you know the uncontroversial facts and can start dissecting the arguments, although always keep a healthy skepticism of everyone's conclusions, including your own.

Simply, be critical and don't simply accept everything you read. It's important to question and understand any source and be critical of it. Read more widely than just one book on something, and skimming Wikipedia on the broad topic can be useful just to get a sense of what debates exist in the historiography, and where the particular book you might be reading sits.

It can always be useful to hunt down footnotes - not in the same way as you might in an academic sense, but if you see something interesting, just to see where it came from.

Related reading or similarly named sections in books can be quite handy too - you can find other books on a particular area that might interest you.

That and sometimes there's no 'right' answer as such, simply differing interpretations, and you should be wary of those who claim otherwise.