Much of the pleasure of reading a diary is the feeling that the writer did not intend us to see it. Even those journals kept with an eye on posterity do not pretend to be novels.
There's a contradiction at the heart of the diary-novel - the most personal thoughts need have no beginning, middle and end. They don't need contrasts, or conflicts, or resolutions. It doesn't matter whether they are well paced. And who cares about inventing interesting characters?
Readers of novels also benefit from digressions, descriptions, and varying viewpoints. Most books written in the first person suffer from some of the same limitations as diaries, but good writers can get round them.
Fictional diaries, however, have to be in diary form and use diary language. So personal pronouns fall away and exclamation marks sprout while the narrative becomes clotted with the filling-in and exposition that non-fictional diaries do not need, because the assumption is that no one is reading them.
All kinds of people write diaries - kings and queens, politicians, scientists, writers, housewives, teachers, painters, good people and bad. One of the chief joys of reading a real journal is the glimpse it gives into another world.
Being able to experience more than one life is one of the great pleasures of reading novels, too, but in the teenage-diary novel, the narrator is always a teenager. This produces, after you've read a few, a sort of Groundhog Day effect. The teenage narrator always has: (a) parents (difficult, embarrassing, ultimately kind); (b) siblings (ditto - and, ditto, ultimately loveable); (c) friends (more variety here, with one friend sometimes being ultimately untrustworthy, and often going off with (d) love object (usually not who you first thought was THE ONE); (e) schools (usually ghastly); (f) teachers (ditto, but can be comic characters); (g) pets (lovely, amusing, cuddly, naughty).
Teenage diarists are always articulate, and some are hilarious. Their style is wise-cracking, fast-moving and their lives could never be reduced to entries reading: "Got C minus forgeog."
Diary-novels have their own conventions and traditions, which seem to have been set by Sue Townsend, who wrote the wonderfully witty and successful Adrian Mole books. These encompassed rather more age groups and social classes than are found in most teenage diary-novels. Helen Fielding has done her bit with Bridget Jones, and all other diarists hope to follow.
Townsend and Fielding's books are funny, clever and easy to read. Teenagers, more than anyone else like easy-to-read books, and main characters with whom they can identify effortlessly. Don't they all want good friends, kind parents and, above all, LURVE (as Ros Asquith's Teenage Worrier would say)? Of course they do. These books won't stretch their minds, but will give them a lot of fun. Perhaps also, readers will go on to Adrian and Bridget, J D Salinger, Robert Cormierand others.
This recent crop of diary-novels all have something to recommend them. My favourite was The Teenage Worrier's Worry Files (Corgi pound;4.99). Ros Asquith's Worrier, Letty Chubb, has a touch of the Molesworth about her, and Asquith's style of illustration has something of Ronald Searle. There are other Teenage Worrier books in the series, with trademark eccentric spelling. I admire a writer who can manage "campaigner" but has trouble with "etc". More happens in Letty's life than in many, and I've lost my heart to Rover the cat.
Yvonne Coppard has had the excellent idea of letting us see the simultaneous diaries of Jenny and her mother in Not Dressed Like That, You Don't!, also illustrated by Ros Asquith and now reissued (Piccadilly pound;5.99). It might seem an obvious device, but there's nothing wrong with a small glimpse of how things look from the other side and readers will be surprised at how often mother and daughter say the same thing in different words.
Kathryn Lamb's More of Everything According to Alex (Piccadilly pound;5.99) profits from the author's own good cartoon illustrations and I liked Alex's friends. Samantha Rugen's Jasmine Fitting In (Piccadilly pound;5.99) is the straightest account of this bunch, and gets extra marks for not even trying to raise a giggle a minute in this tale of Jasmine, an engaging hippyish teenager, fond of crystals and horoscopes.
Perhaps the main function of this sort of book is to echo the experiences of the reader: to make teenagers feel they are not alone in the desert wastes of adolescence. In which case one has to say, reluctantly, the more the merrier.