One of the hardest parts about exploring a new and relatively obscure topic as an adult is figuring out where to start. (Relatively obscure=any subject you can't take a class on at community college or find a basic For Dummies or similar introduction.) It's not always easy to find the bridges that take you from basic, wikipedia-article knowledge to the kind of expertise you need if you're going to write about a topic yourself. I've frequently requested books from interlibrary loan or shelled out my hard-earned money only to find they're barely more informative than a wikipedia article or else are way over my head.
Way back in 2003 or so when I was first developing the plot for The Sergeant's Lady, I realized I needed to know a lot more about all aspects of Napoleonic-era army life. One of the first books I tried was Tactics and the Experience of Battle in the Age of Napoleon (Rory Muir, 1998). And at the time, it was way over my head. I remember being baffled by the terminology, as if each paragraph was a thicket of thorns I was trying to push through.
Four years later and many research hours later, I tried it again...and found it easy reading. Informative, but easy. So I guess I've been learning something after all. That's encouraging, really--that my mind still has at least some of its collegiate flexibility despite being so busy and out of practice academically.