I voted for Amber. The second set of 5 is a bit weaker than the first set of 5, but they're great fun. One of those series that make you wish things were really like that.
My second choice would be the Nevil Shute. I haven't read it yet, but I'm fairly confident that it will keep you engaged. I don't follow the book club threads, and didn't realise this was next month's pick. I have a complete set of Shute pbooks of various vintages I inherited from my father, and might join in. The only one I've read so far is No Highway, about this time last year, and I really enjoyed that.