Each book does have some impression on you and some can be read again and again for their entertainment value.
My books that I have read multiple times are
Doctors - Erich Segal.... Like someone said a must for all doctors to be and all of us can relate with one or the other character at sometime in life
Roots - Alex hailey... for the sheer genius of the author and his narration. It is a gripping tale, a must read
King Rat - James Clavell. Dont know why but this small novel attracts me a lot for the protagonist/ antagonist at his fate in the end.
Harry Potter and Inheritance series from the fiction fantasy genre
Recently read Still Alice about Alzheimer and the fault in our stars, then tuesdays with Morrie........
there are so many of them......
Jeffery Archer, Ken Follet, Friedrich Forsyth, Robin Cook, Robert Ludlum, Arthur C Clarke, Carl Sagan, Michael Crichton, John Grisham...... These are authors which give you joy of reading. I think I have read through all of them and have repeated many.
I have the hard copies of almost all of them ..... Thats something aint it