Check out The Thirty Years War: Europe's Tragedy by Peter H. Wilson . I'm not a scholar and I'm obviously not flaired, but I read this book two years ago and, though it can be a bit of a slog, I haven't found anything better yet about the subject apart from primary sources.

Just a hobbyist as well but hopefully this helps.

I just received a copy of Essential Histories The Thirty Years' War 1618-1648 by Richard Bonney and my initial impressions on a thumb through are: very thin - under a hundred pages with lots of pictures and blank space, probably good for a quick overview, lovely portraits/battle maps/artworks.

I would recommend it for a light read but probably wouldn't pay full price for it. I see it used for $8.00 on Amazon (although I didn't check shipping) and that seems a fair price for what is, essentially, a magazine worth of reading.

That time period also covers the English Civil Wars for which I would recommend Christopher Hill's The Century of Revolution. I believe Hill is well regarded around here.

I second the The Thirty Years War Europe's Tragedy that is not my area of expertise and that is the book that I read to get a nice overview of the era. Another book that should be at your library that could give an overview is Iron Kingdom. The Rise and Downfall of Prussia, 1600-1947. Obviously just read the start and then stop.