Childhood's End Great buildup, disappointing finish.
Stranger In A Strange Land Too weird. Haven't quite finished it yet. Heinlein, like Clarke, falls apart when he tries to write interpersonal relationships and dialogue instead of straight prose.
The Idea Factory. An excellent history of AT&T, Western Electric, and Bell Labs.
Anatomy Of A Dictatorship: Inside The GDR, 1949-1989. Just picked it up. I made it through the first chapter, and this is an excellent book so far.