I reread favorite books and series all the time - have always done so. I'm talking about printed books here, because I haven't had my Libre long enough to even go through them once yet.
I'll usually reread an entire series every couple of years. They are series that I enjoyed reading the first time around, ones that successfully created their universe in my mind to the point where I can easily visualize the settings, the characters and the scenarios.
Some favorites are:
Eric Flint's 1632 series (with the supplemental collections and gazettes)
David Weber's Honor Harrington series
David Weber & John Ringo's Prince Roger series
Sharon Lee & Steve Miller's Liaden Universe series (including prequels and offshoots)
Suzanne Brockmann's SEALS/Troubleshooters series
C.E. Murphy's Urban Shaman series
Janet Evanovich's Stephanie Plum series
Catherine Asaro's Skolian Empire series
Other authors that I always reread on a regular basis are Georgette Heyer, Charles de Lint, Carolyn Haines, Charlaine Harris, Julia Spencer-Fleming, Sandra Hill.
But really, whenever I open up one of my plastic storage boxes of book, I usually wind up rereading half of them.
I like the comparison that was made earlier in the thread, comparing favorite books to favorite music. I think that is very apropos in my situation. It's not that I've forgotten what I've read, or that I reread to discover something new in the story (I mean, after 3 or 4 times there's usually nothing left to discover when we're talking genre books). It's just that I enjoyed the books so much the first time that the enjoyment always remains, and I know that I can lose myself in those stories for a while and escape all the cares and worries of everyday life. The same applies to favorite music; it serves to evoke a mood I want to re-experience.