I'm listening to the audiobook and am only to the part where George/Jake reveals his true mission and who he is, to Sadie, so I don't know the ending.
Regardless, I have the perfect actor for Jake/George A. - John Hamm.
Firstly, he's a little older but who cares. He already has that middle 20th century swagger down in his current hit series role, he's a good actor, and I could see him playing the sort of reserved maybe even timid teacher Jake but also being the man who can be tough and kill when he has to as George. It would be cool to see him with long hair in the 21st century and then have that same slicked back hair in Mad Men driving in his hot convertible when he goes back in time. In my opinion, the movie shouldn't be exactly like the book because honestly, I don't think this book translates well to a hit movie if done exactly the same If the actors are off a little by age, physical description, etc....who cares.
Sadie - Reese Witherspoon - adorable and could pull off a sweet, sexy yet naive Sadie. Oh Oh Oh Suga!!!!!!!!! ..height not important.
Deke - Tommy Lee Jones - He can play a tough ol Texan bastard who'll go have a ****ty beer with ya!
and to throw in some former Steven King book to movie alumni
Al Templeton - Jack Nicholson Ok, you say "too old"? Well, if the actor is older, there are many possibilities, such as his life has run out due to old age and he must pass the torch to Jake...which essentially is the real story or he made several attempts at changing the future, but failed many times. Hollywood can do their magic to make the actor look younger/older and healthy/sick from one day to the next.
or James Caan - same as above concerning age..
or Tim Robbins - My pick if sticking closer to script..very good Actor. Just realized he would also be good for Jake/George, even though he'd be older than the book character.
Ellie Dockerty - I don't even remember her age or physical description in the book but I keep thinking Kathy Bates!
...I haven't really thought about the other characters.
Man I must be bored today...