'I Spy' is also a series of picture books that are more like games than actual books to read. Every 'I Spy' book contains about 12 two-page photo spreads of toys. The toys are hidden behind objects, and frequently arranged to form a model or scene. At the bottom few inches of each page, a sentence starting with "I spy" lists the objects you are supposed to find in the scene. There are usually about 12 different things to find in each picture.

Each book has a different ongoing theme, and a subtle plot that many children don't catch on to. For example, in 'I Spy: Haunted House', one picture may be of a library, and the next picture could be of a specific bookshelf in that library. In haunted houses, it is common knowledge that pulling a certain book on the shelf will reveal a secret passage, so that secret passage would likely be in the third scene.

These books can take over an hour to solve, depending on the sharpness of your eye. Similar to the 'Where's Waldo?' books, the largest problem is the book is only enjoyable once, and then worthless when you have found everything. Luckily, the 'I Spy' writers have found a way around this by making more books. The 'I Spy' library currently comprises of 19 books, which have been listed here in their entirety (and alphabetically, too!).

  • I Spy
  • I Spy: Christmas
  • I Spy: Extreme Challenger!
  • I Spy: Fantasy
  • I Spy: Fun House
  • I Spy: Gold Challenger
  • I Spy: Little Animals
  • I Spy: Little Book
  • I Spy: Little Bunnies
  • I Spy: Little Christmas
  • I Spy: Little Letters
  • I Spy: Little Wheels
  • I Spy: Mystery
  • I Spy: School Days
  • I Spy: Spooky Night
  • I Spy: Super Challenger!
  • I Spy: Treasure Hunt
  • I Spy: Ultimate Challenger!
  • I Spy: Year-Round Challenger!

The stories and the rhymes are written by Jean Marzollo, and photographs of the toy arrangements are by Walter Wick. Titles including the word 'Challenger' obviously contain more difficult puzzles, and titles with 'Little' are meant for younger kids, such as age five or so. All other titles are suitable for ages 6 and up, since the puzzles can be fun to play for young and old.