What's best bookshelf speaker for an 8x10 room?

The Vandersteen Model 3 would be my first choice.

Several will work well in spite of what some will tell you.
Spendor and Harbeth are the two most popular choices.
Linn monitors work in small rooms.
I have the same size room, right now using Kudos Super 10.
But also have a pair of these:
http://guruaudio.com/
I would recommend them

Without knowing what amplifier you have, it would be impossible to recommend a speaker; even if was being used in a small room. Besides, speakers are so subjective, what sounds good to one person, may not sound good to you. If any component needs to be auditioned, its certainly speakers.

Also, you indicated you are going to use them on a bookshelf. Therefore, you need to look at front ported speakers only. If you press rear ports against a wall, you won't be getting all the bass the designers intended. For example the Kef LS50's that were suggested, are rear ported and those ports should be 18"-36" away from a rear wall. And I have never seen a shelf that deep.

So my suggestions is to know your amps capability, makes sure it matches the impedance and sensitivity ratings of what speakers you are auditioning and consider front ported models only. A far more intelligent approach to find the speakers that are best for you. Good luck and rock on brother!

BTW
my recommendation above is for the Guru Juniors only. They are meant to be placed right against the rear wall, or in a bookshelf