1632, something I'd put off for years. I have a love-hate relationship with alt-history fiction. When it's really good I enjoy it a great deal. When it's bad, it makes me crazy. To avoid being driven crazy by what might be bad alt-history set in one of my favorite historical periods, I've studiously avoided this series for quite a long time.
This is not bad alt-history.
First, from a historical perspective, Flint knows his history. The period is depicted very well. There's decided bias toward certain factions in the Thirty Years War but it's a bias that I happen to agree (rather strongly) with, so it didn't bother me. It is also rather strongly pro-American common man (and woman), an attitude that might not be terribly popular in a lot of circles these days given the recent election.
Nonetheless Flint gets his history right. He depicts the horrors of the Thirty Years War accurately. His characterization of the politics of the period are simplified, but he isn't writing a scholarly paper but rather adventure fiction, and from that perspective, they're good enough.
In terms of plot and characterization, it was about what I expected for a novel in this genre. There are no great truths in this book, but there aren't supposed to be. What it is, is great fun set in an historical milieu that is interesting to visit but would have been hell to live in. The military-oriented scenes are a great pleasure to read. I enjoyed that Flint depicted even the enemy soldiers sympathetically for the most part rather than making fun of the tactics of the time. The description of the Battle of Breitenfeld was particularly well done. Also, nearly the entire novel is set in Thuringia, a region I've grown well-acquainted with over the past few months. I'm engaged in an ongoing online Kriegsspiel game of Napoleon's 1806 campaign in the area, and several several PBEM games of Tiller's Campaign Jena-Auerstadt. The region is also important during both the War of Spanish Succession and the Seven Years War.
The novel is unquestionably escapism but it's a fun read. Beyond that, 1632 strikes me as the true heir to H. Beam Piper's Lord Kalvan of Otherwhen, one of my favorite SF novels of all time. Geographically the fictional town of Grantville, West Virginia from 1632 is set in the same Appalachian mountain country as the alternate Pennsylvania of Piper's Hostigos. Ultimately it's worth a bit of a think to contrast the "supremely competent individual" philosophy of Lord Kalvan with the "it takes a village" message of 1632, but no one should probably ever construe that there's much of a deliberate message in either, or that 1632 is in some way an answer to Piper.
If you enjoy SF and history, particularly the Thirty Years War, definitely give 1632 a read. It's a nice break from trying to wrap one's head around one of the more complex conflicts of early modern history when reading serious history.