The Sweet Far Thing, by Libba Bray, was just as enthralling and amazing as the first two (A Great and Terrible Beauty as well as Rebel Angels). It was a long book (819 pages) but I loved every minute of it. Once again I can't give you a very good summary if you haven't read the first two because I don't want to give anything away. But I'll say somethings about it...
Some authors have a really good series, but then when they get to the last book, they end it, well, not the best way. Libba Bray did NOT do this!! She had a phenomenal ending to the great trilogy.
I loved the constant controversy of Felicity and Gemma, and their disagreements are hilarious, and if you haven't read the book and just flipped to a random page, you'd think they were mad! ;-) A few characters I really enjoyed were; Wendy, Kartik, and Fowlson (especially Fowlson in the climax). Parts of it were like a mystery, and the History of Secret Societies, by Wilhelmina Wyatt are found to have some possible clues.
Mrs. Nightwing, the current headmistress at Spence Academy, becomes a lot kinder to Gemma, and I loved her during The Sweet Far Thing.
Other than the climax, my favorite scene is when Gemma finds the Tree of All Souls. Libba Bray is such a talented writer, she describes it all so well! I wish I could say more, but then I would reveal the secrets that make this novel so great. Life and death, truth and lies, or good and evil, all of it is mixed together in Libba Bray's third book, A Sweet Far Thing. One of the best book series I've ever read!