Hello! I write from Italy. Here, at the university, during the first year every student had to take a general exam on "roman history", "medieval history", "modern history (1492-1789) and "contemporary history". Potentially, you could also take a "greek history" exam. For each of this exams we had a manual, which is a tome with the general history of the period (still pretty eurocentric tomes, mind you) and we could choose several monographies on more specific subjects.

Now, reading a general manual may be useful, but also extremely boring: since manuals have to synthetize a lot of stuff, often they are really a lot of names and a lot of dates. So I wonder, isn't there some subject that interests you in particular to begin with?

You could simply start from the there, having a look around to which books may be interesting for you to read. Sometimes a monography about an apparently specific subject will tell much more than you'd have imagined to read and could start new interests. For example, when I read "The reason why" by C.W. Smith, a pretty dated book about the "Charge of the Light Brigade", I wanted to know more about the episode because I had just seen the 1968 movie. When I finished the book I learned a lot more than I imagined about the victorian british society and the irish famine, because both subjects are somehow related to the episode. Both subjects I could furtherly explore by reading specific books on them. By reading those books, say, a book on the irish famine, I could have learned some irish history. Maybe, reading about irish history, I could have learned about Cromwell, then I could want to know more about the English Civil War and other subjects would came out, and then I could check them out just as well and so on and so forth.

The best thing you need to check to have an idea about the reliability of the book is the bibliography: how many primary sources (i.e. documents written DURING the historical period) are featured? and how many secondary sources? You may also want to ask to yourself: when was this book written? is it up to date with the current debates? Last but not least, who wrote the book? Knowing who the author is will surely help you understand his point of view and how he came to the thesis he brought up in the book. In history you can never take for granted what you read by a single author, you should always check and compare with others.