One of my biggest passion beside photography, it's to get lost in bookshops and libraries. My eyes were attracted by a book called "The Photographer's Playbook" and especially seeing the publisher "aperture" which is usually an incredible publishing house for photography books.
The book is composed of 307 assignments and ideas for photographers. Don't be scared, it's not a schoolbook. It's basically ideas or advices given by wellknown photographers to their students.
There are lots of them and even if you don't like some, you can skip to the ones you like.
Some ideas are really refreshing like the one from Elisabeth Tonnard which uses the text of Roland Barthes "The Death of the Author" and propose to replace each occurence of words like "words" with "images" or "write" with "take photographs". Then she proposes to use the resulting text as a trigger for your photographic works.
Some are meaningful notes that can be used as day-to-day support like the ones from Denise Wolff or Alex Klein.
A great companion book for any photographers willing to be enlighten or shaken by random notes or ideas.