Handy site with suggested reading guides for various book series or comic book series.
(I was looking for the reading order for the Percy Jackson books and this site came up!)
Not a huge site but series such as Buffy, Grantchester, Discworld, Jack Ryan, Rivers of London (which is another I want to get into), Constantine, Green Lantern etc....
Hope someone finds it useful!
Edit: Only just noticed there is a search bar low down on the right hand side of the page. That helps a lot.