The cover designs of O'Reilly books are truly awesome (and I don't use that word often). They are not only recognizable in a "brand" kind of way, but they are

The cover designs of O'Reilly books are truly awesome (and I don't use that word often). They are not only recognizable in a "brand" kind of way, but they are also professional looking, simple but with a twist of the creativity that differentiate programmers from other technical professions.