The Gone-Away World, Nick Harkaway: YES YES YES. Like a dystopic Catch-22, full of black humor and tongue-dazzling wordplay, a great end-of-world-and-after scenario, and wonderful characters. Destined to be a classic--and unlike back-of-book blurbers, I do not use that phrase lightly.
Hotel Iris, Yoko Ogawa: I've read three books by Ogawa now (I think that's every one translated into English so far) and they've all been wildly different, but all stark and beautiful. This one is very dark, about the BDSM relationship between a 17-year-old girl and a man fifty years her senior. Point your mom towards The Housekeeper & the Professor instead.
The Boneshaker, Kate Milford: Middle-grade steampunk FTW! Full of creepy automatons, snake oil salesmen, and deals with the Devil, with an appropriately plucky heroine. Loved it.