Well first off I like Turtledove books, usually. I just finished the Hawaii duo, they were good. I started years back with World War but it fell foul of the thing that puts me off Turtledove. It goes for too long. 3 books in the original series, then 2 or 3 books in the continuing one after that then the final book. I get bored with them if they go on too long, but I did get Homeward bound, the last one, which I was dissapointed with as nothing really happened.
Timeline-119 (CSA series) I read but again got bored with and quit, that and analogous stories don't thrill me, though I am playing a mod of it in a WW2 game.
I do like Turtledove though, but only when he limits it to 1 book or 2. "Guns of the South" is one of my favourite books. Afrikaaner white supremacists go back to civil war and give Confederates Ak-47s. Sounds cheesy but Turtledove can pull it off well. SM Stirling is similar to Turtledove, but I have avoided his counterpart to the "Sea of Time" where electricity stops working.
Other authors I generally buy anything they write are Terry Pratchett, Peter L Hamilton (not his one offs but the series) and the late David Gemmell (pity I'll bever get a new book from him
)
I usually go for large books if I can get them. I am a speed reader of sorts (not learnt, just the way I read) so I want books that will last longer than 3 hours.
I split my reading time between fiction and essays. Currently I am reading a sci-fi, Watch on the Rhine, a Star Trek novel with the Mirror Universe, and 2 texts, Counetrfactual thought experiments in world politics, and Unmaking the west- essays in world counterfactuals, both by the same editor. Those 2 might be a bit dry though as they are published by Princeton university. I actually have quite a few books that are peoples doctoral thesis.