First question: Do all tomes look brown and all books look orange?

Second question: Is there a tome for every ability (e.g. strength)?

Third question: The tomes in Candlekeep, just how many (just amount) USEFUL tomes are in there?

The answers to this next question are the major spoilers... I'm probably not going to even look at the answers to this one but I just want it available to whoever might need the answers.

Where are each of the USEFUL tomes found?

I know of two !SPOILER SPOILER! One is the tome of health (constitution) in the sirine cavern south of Candlekeep. The other is the tome of charisma (forgot the name) in a cave south of the gnoll stronghold. !SPOILER SPOILER!

Question 1 - Yes, Tomes look different than books
Question 2 - Yes for Strength, I don't know about EVERY stat. I remember Tomes for Strength, Intelligence, Constitution, and Charisma.
I don't remember how many there are or where they are. I think the wizard's tower in the city has one.
Sherpa Doug

All tomes have a similar, yet unique (to other books), look to them - at least for BG. But I think TotSC has 1 or 2 quest items which look like the tomes. On the other hand, TotSC only has one tome in question, which is the Tome of Wisdom.

Qn. 2: Yes, there is (at least) a tome for every stat (the 'at least' applies only to Wisdom , though)

Qn. 3: 2 tomes.

Location of the tomes:
*
*
*
*
*
*
*
*
Str: Under Candlekeep (1st level)
Dex: East quadrant of BG city, in the Thieves' Guild, in the barrel near the female thief selling you goods.
Wisdom: West quad of BG city, in the temple of Tymora - just talk to the priestess
Another one can be found under Candlekeep, near to the Tome of Strength.
Int: Nort quad of BG city, top level of wizard's (Ramazith's) tower.

After searching a while I've come on the info where all the tomes are, some of these have already been said but here they are in a neat little order .

(First of all, all I know of though all my looking is one tome for every stat and no more, never seen two tomes of wisdom. Although I'm getting a strong sence your right now... These are in order of when you can get them.)

Tome of Constitution - Sirine Cave - S of Candlekeep

Tome of Charisma - A box in a cave - S of Gnoll Stronghold

Tome of Intelligence - Top floor desk/bookcase - Razimath's Tower (tall tower in northern section), Baldur's Gate

Tome of Dexterity - In crate/bag in easternmost room of the back area of the Thieves Guild near Black Lily - Thieves Guild (north of sorcerous sundries in a building cluster, password starts with an f), Baldur's Gate

Tome of Strength & Wisdom - Catacombs under Candlekeep after being imprisonated in chapter... 6? - Candlekeep