The Lord of the Rings

Yes, Jazzo! That would be it for me!...including The Hobbit as prologue.
And I guess Atlas Shrugged would have to be yours, required reading for an aspiring architect! Alas, that was another intended but never embarked-upon long-read in my life...actually leafing through it a number of times trying to convince myself to get started.

[edit: I had to fix a misspelling--embraked-upon for embarked-upon...but the typo coinage fits if you think about it. A subtle subconscious intention? ]