Part A: Digression on History, Metaphysics, and Graduate School

Don't worry too much about your reading habits, at least not yet. It takes a more special person than is often acknowledged to read through masses of material without a question in mind. A mentor once told me that "...as odd as it sounds, questions precede content." What does that mean in practice? It isn't a metaphysical thing, some sort of admission that the real world is the product of our minds. Rather, it strikes at the observation that our sources are limited in what they can tell us on first analysis compared to what you'll eventually want to know. The thing that you'll want to know can't be known from positive readings of the sources, so you'll have to make up the distance by asking reasonable questions about the nature of the space between our sources. Your questions, in what should be a controlled manner, create and imagine that space. Thus "...questions precede content." For me, and this is all to our point, this draws into sight the idea that content without a question sometimes misses the meat of history altogether: it runs a greater risk of becoming unstructured and unanalyzed data, which the mind doesn't hold well. Reading gets better as you find things to read for.

So, at this point, you might ask: "Habron, that is super ridiculous. Obviously historians read a ton. A lot of it is super boring, but they do it. What do you expect me to do?" Two things, I guess. One, people read a lot of things that are grinds in graduate school and beyond. Getting something substantial out of that, out of reading something that you're reading for the sake of acquiring knowledge rather than answering questions, is a lot harder and requires its own tools, often involving repeated rereading and lots of notes. You don't need to do that yet. Someone (an advisor) will make sure that you know. For now (the second thing) the best thing that you can do for yourself is not that. Just read things that are interesting to you. You're not going to be judged at the start of an MA if you don't know every argument of one of the great works. You might impress people if you have a lot to say about something you enjoy though. Don't let yourself get discouraged if grasping onto what you're reading doesn't work out every day. That's just how it goes, but it does get better.

That's my big advice on life. Other people around here might disagree with me, and that's probably for the best!

Part B: Actually making an effort at answering the question

Bloch, Marc. Feudal Society, Two Volumes, L. A. Manyon trans. (University of Chicago Press, 1961).

Bloch is worthwhile as the representative of the French Annales School. He makes big claims that are often not upheld anymore, but remains an important person for more than historiographic reasons. Read with skepticism. Parts of the work do concern the period that you're interested in, and, in any case, you should try to develop some ideas on the long view about how the early Middle Ages exist as a distinct period in relation to Late Antiquity and the Middle Ages "proper."

Pirenne, Henri. Mohammed and Charlemagne (Dover, 1954 [2001])

Another work representing an important but more or less discredited thesis. Pirenne argues (the "Pirenne Thesis") that the Germanic invasions of late antiquity were not the crucial factor in causing the rapid diminishment of the Mediterranean Sea as a space of trade, culture, and communication; he believes that the Islamic Conquests brought this about, leading the political balance of Europe to shift from the Mediterranean to "Charlemagne." It's interesting and easy reading. Again, be skeptical.

There have been a number of massive tomes about the Early Middle Ages in somewhat recent memory. Two good ones to have on your radar are the following. Both McCormick and Wickham are real masters, so, in contrast to my previous references, they give nice hints at where the field is today.

McCormick, Michael. Origins of the European Economy: Communications and Commerce AD 300 - 900. (Cambridge, 2002).

Wickham, Chris. Framing the Early Middle Ages (Oxford, 2005).

I'd also recommend looking at Wickham's "The Inheritance of Rome" over either of the prior. It is less of a magnum opus type work, but focuses on providing broad thematic and regional overviews in a way that is helpful and (important) can be intelligibly read as chapters rather than signing on to read 1200 pages (which is sometimes fun!).

Others will have other ideas. I'll close by repeating my starting advise: don't sweat it too much right now. Find things that you want to read. Shamelessly abandon things that you don't. Have fun!