If you are interested in sup-norm and Hölder estimates, then Lunardi's book is a good start:
Otherwise you should specify what type of equation are you interested in.
ADDED: Afret the comment of @Liviu:
You should not omit Krylov's books from your list: the one on Hölder spaces and the one on $L^p$ spaces.
And of course there is Evans. An excellent introduction.
ADDED: After the clarification in the question: Topping's lecture notes (there is also a book version from the London Mathematical Society) are quite nice and readable.
