Been reading Norman Friedman's "US Submarines Since 1945: An Illustrated Design History" for the third time because I'm a glutton for punishment. Actually, I really do enjoy it, it's just EXTREMELY detailed and dense.
I also recently finished reading Bill Yenne's "Building the B-17 Flying Fortress." Kind of dry, but the selection of photographs is incredible. You can read my review here:
https://www.amazon.com/gp/aw/review/...at_pdctrvw_srp