There are a total of 17 guide book pages in Dead Island Riptide. Finding all of them will earn you the "Professional Tourist" trophy or achievement. In the inventory you can see which collectibles you have already found. They are all numbered and you can identify missing collectibles easily. There is no free roam after the story ends, so you have to collect everything before completing the last chapter.
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via N4G: pc news feed http://n4g.com/news/1241387/dead-island-riptide-all-guide-book-collectible-locations