By weight single volume? I’ve got a very heavy leather bound works of William Shakespeare. It doesn’t use the really thin pages that these editions typically have which just makes it a monster that weighs a ton.
By weight bound set? The complete Calvin and Hobbes which is like the The Far Side set mentioned above.
By page size? Science Fiction of the 20th Century which is about 20x14.
Dimensions: an atlas. I can’t offhand remember the title.
Weight: Toss up between the Macquarie Dictionary and an algebra textbook.
Complete Works of Shakespeare. It’s one 6" thick oversized book with tissue thin pages. That was real fun to lug around campus. On the bright side, if anyone had bothered me after dark, I probably could have maimed him with it.
In my house, but not exactly mine, is a massive single volume encyclopedia from the 50s or 60s: 15"x10"x8"
Bowers et al., Actuarial Mathematics 2e. It’s actually only about 650 pages, but it’s printed on very heavy paper; however, I think it wins for sheer misery, as those sitting for the third actuarial exam are expected to pretty much memorize most of it.
Audubon’s Birds of America
If you mean dimensions, there’s a book on the history of China as seen by the West that’s 10 x 15 x 1.25.
For volume and weight, The Baseball Encyclopedia
Ditto.
If you want pages, it’s my OED.
and
Webster’s Third. 12.5 pounds, 4 inches thick, 2,662 pp.
I had an enormous Times Atlas of the World from 1984. But I replaced it with a smaller one and gave it to my sister. I never measured it but it was much, much larger than my current largest tome
Cabinet of Natural Curiosities
19.8 x 12.8 x 3.5 inches
16.4 pounds
I wasn’t sure if dictionaries or multi-volume works counted. If dictionaries count, mine is the Encarta dictionary. If multi-volumes count, it’s the big Universal Press comic sets, Far Side and Calvin (heck, even Gary Larson joked his book could double as a murder weapon).
I have a single-bound copy of the Summa Theologica from 1947 which weighs 10.8 pounds and measures 8" x 12" x 6". I bought it in a used book store for under $20. Between its mass and how often I need to research Catholic philosophy on a day-to-day basis, it doesn’t leave the bookshelf all that often.
Do multiple volums count? If so, then *Remembrance of Things Past * or *In Search of Lost Time * (depending on which title one prefers), by Marcel Proust.
By far, the tallest book we have is A Century of Thai Graphic Design, compiled by Anake Nawigamune. The thickest single volume we have is A New English-Thai Dictionary, 1899 pages of VERY small print.
The thickest regular book seems to be a tie between *The Lord of the Rings * (all three books in one volume) and a hard-cover copy of Harry Potter and the Order of the Phoenix.
Jay P. Green’s Hebrew-Greek-English Interlinear Bible and Barry Moser’s edition of The Holy Bible
Telephone.
And most of it, I’ve never even read.
The butler did it.
Dang, never saw that one coming.
Was it the substitute butler they sent over from Zzygy’s Emergency Domestics?
Leonardo Da Vinci, 14.5"x11"x2.5", dunno how much it weighs, but it be heavy. It’s an exact reprint of a volume issued in 1938 for what was the very last Leonardo exhibition the world will ever see (it would just too expensive to do one now).
As a matter of fact. 
I own the tenth edition reprint from 2001. It measures 18" x 12" x 1.5". I think the atlas weighs about 13lb but I’m unable to confirm this because it just broke my scales.