First, I am sorry that this is a broad question, but I don't know enough about the subject to narrow down my question.
Recently I read the book 1848: A Year of Revolutions by Mike Rapport, and now I'm reading Sarum: The Novel of England by Edward Rutherford.
While reading these two books I realized that even though I majored in History, I only have an understanding of modern Europe and it is centered on whatever Britain was involved in at the time. In the 1848 book there are several chapters about eastern Europe and I want to know more about all of the different nationalities and from where they came. For example, the book discusses Slovaks, Czech, Serbs, Croats, Magyars, Romanians, Saxon, and Prussians and other Germanic people.
In Sarum, the book starts in England before Stone Henge is built and continues on with the different people that come from the continent to England up until modern times. This made me realize that I don't know anything about the migration and evolution of the different people of Europe. Who where the Anglo-Saxons, Franks, and other early European people. What other groups were there? Where did they come from? What other groups evolve from these people? I understand that this covers a very long period of time and that it extends to a time where there might not be a lot of information, but I'm very curious. Do you have any resources or books that you recommend so that I can start learning more about the first peoples of Europe and how they evolved to become all of these different nationalities with different cultures and languages that appear in modern History?
What I really want is to set a better Historical foundation for myself. I am aware that this is a gigantically large period of History, but any direction would be helpful. I looked at the Book List but there didn't seem to be any books that describe what I want and the Popular Questions list didn't provide anywhere for me to start learning on my own.
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First off, I'd recommend Pat Geary's Myth of Nations (2003). It's a really good review about why we talk about nations, even when there's little evidence that people before the 1800s (even up to 1848) thought of themselves as belonging to ethnic groups.
If you'd rather dig into a bit more about who the early Franks and Germans really were, I'd recommend Pat Geary's Before France and Germany (1988). Guy Halsall's Barbarian Migrations and the Roman West (2008) is a much more thorough and up-to-date survey, but it'll require some patience (and perhaps a bit of help from Google and Wikipedia to get your groundings) if it's your first introduction to the peoples of early Europe.
Finally, if you're interested in prehistoric Britain (Stonehenge and all), I absolutely love John Barrett's Fragments from Antiquity (1994). It's a tough but very rewarding read.
Any good comprehensive history of Britain will include information about the (as far as we know?) indigenous groups who inhabited the British isles before the arrival of the Angles, Saxons, and Jutes. If you're looking for something other than another book, this is covered in the first episode of Simon Schama's A History Of Britain documentary series, as well as the first several installments of the History Of England podcast.
Since pre-Roman Britons didn't have a written literary tradition, you might have better luck researching British archaeology (probably Iron Age or neolithic) rather than history per se.
Regarding the origins of all the other people on the European continent, it's a complicated mix and you'll have better luck researching specific groups. A quick one-sentence answer is that most of the nations and major ethnic groups of Europe trace their history to groups the ancient Romans came into contact with. If you look at a map of "barbarian" tribes surrounding the Roman empire, a lot of the names look like names we associate with European "nations". You've got the Franks, the Alemanni, the Lombards, the Belgae, etc. However, each of these groups has a different history, and it can't really be generalized. One thing to know is that the current thought, thanks to studies of modern population genetics, is that the "Barbarian Invasions" didn't necessarily have a strong effect on the population makeup of Europe. It's better to think of these groups as national self-identities and factors in the cultural narratives of various European populations. Except for maybe the Magyars and the Basques, but they're special cases in general and yet another good reason to read up on different European cultures separately, in more depth.
Excellent idea! However, what you're asking for could literally fill several books, and I doubt the ability of any one of our flaired users to answer it fully. Have you considered audio lectures? I found the lectures from The Teaching Company immensely useful in developing base level understandings of topics such as this. You can purchase them from Audible, if you're so inclined, and at about $12 a pop (for 12-24 hours of lecture by a professional historian) it's fairly affordable.