Last Wednesday I recommended a real diary because it helps to be familiar with the non-fiction diary form when reading fictional diaries. In fiction the diary form has been used to good effect in parody and for satire, but also for more innocent humour. It has also been used in dead earnest in fiction. It is one of the forms which epistolatory novels take, a sort of monologue where the reader takes on the role of the narrator's confessor.
Here are some that I can recommend:
- The Secret Diary of Adrian Mole, Aged 13 ¾ and The Growing Pains of Adrian Mole by Sue Townsend. These are ostensibly written for teenagers, but can be enjoyed by adults as well. I have not read the sequels, but I do own them and plan to read them.
- Bridget Jones's Diary by Helen Fielding.
- Angus, Thongs and Full-Frontal Snogging by Louise Rennison. Written for teenage girls, but quite enjoyable. Have not read any of the sequels, but expect them to be enjoyable as well.
- The Princess Diaries by Meg Cabot. Another series written for teenage girls, but enjoyable for adults as well.
- I Capture the Castle by Dodie Smith.
Here are some more ideas (from Wikipedia).