I would strongly recommend "Aerodynamics, Engines and Systems for the Professional Pilot"
by David Robson (Airlife). Its sister book, "Avionics and Flight Management for the Professional Pilot"
is also very good - but out of the scope of this particular thread. Over little more than 300 pages, it gives all the info you need in a clear style, with excellent diagrams/graphs etc. Available from the usual shops/internet sellers.
Never been impressed by "Handling the Big Jets"
by D. P. Davies. Why? Well, it's written in test pilot style, only covers jets (so much for those of us flying turboprops!) and definitely shows its age. A book based mainly on the 707, and describing the 747-100 as a "modern" aircraft can be disregarded in 2008. For the same reason, there is nothing in it on FBW, IRS, GPS, (E)GPWS, TCAS, etc. I know a number of recruiters swear by it (that's why I bought it), but then they are also showing their age. I have highlighted the (few) useful bits in my copy, and now it takes me under an hour to read through it!
"Mechanics of Flight"
by A. C. Kermode is very good (and has been thoroughly updated, unlike "Handling the Big Jets"
), but as has been said, is more geared towards aerodynamics. It also includes parts that are useless to most of us, such as supersonic flight and spaceflight. The relevant chapters are worth a read if you get the book at bargain price though.