There are a total of 10 diary collectibles in Dead Island Riptide. Finding all of them is a requirement for the Hoarder trophy or achievement (find all 61 collectibles). 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.
via N4G: pc news feed http://n4g.com/news/1242072/dead-island-riptide-all-diary-collectible-locations
via N4G: pc news feed http://n4g.com/news/1242072/dead-island-riptide-all-diary-collectible-locations