A shot at some portraits

I shot these for a friend of mine who wanted some shots for his physics website, dealing with his dissertation and research goals. He likes the first one, but my personal favorite of the bunch is with the book (despite the cliche nature of the shot).
What does everyone think?

Any comments would be much appreciated

-Chris

Oh, and I forgot to add...
The lighting was sunlight from the left, with a track light from above and in front. Hence the somewhat harsh shadowing.

I like the third one - good composition - nice real life look on his face and lighting seems better than the rest. Good work. All I can say about shooting portraits (my limited experience so far) is practice, practice, practice - and don't be afraid to experiment.