I've re-read all my Famous Five, Mallory Towers and St Clares books recently. They are very dated now, of course, but I still enjoyed them!
I've also read Rebecca by Daphne Du Maurier, Beyond This Place by A J Cronin and Rachel's Holiday by Marian Keyes more than once.
Other than that, I have so many books on my 'To Read' pile, that I feel guilty if I don't concentrate on that!