Any self-respecting book cover geek needs to take a gander at this website dedicated to the cover art of Penguin paperbacks, curated by Australian design instructor  Greg Neville .

“Penguin Books has had numerous categories in its long history: fiction, crime, sci-fi, poetry, theatre, classics, non-fiction, education etc. Alongside these broad categories more specific printings have been made with particular themes. For example, an edition of a particular author’s works, a specially priced series, a focus on regional authors, or series based on food, travel or romance. These editions of related books, where the art direction and design is co-ordinated in a single aesthetic with variations on a theme, is the subject of this site.” As you’d expect there is some gorgeous cover design on display here.