For all non-real world articles, always write in-universe. Basically, pretend it is real historical fact you are recounting, not fiction. Rather than "In the novel Legend ..." write "During the Siege of Dros Delnoch ..."
Use the past tense (again, except for real world articles). Example: "Waylander was a Drenai assassin" not "Waylander is a Drenai assassin".
All information (which is not something general or self-explanatory) ought to be referenced. For Gemmell books, chapter names/numbers are preferable to page numbers, as the latter can differ between editions. For help with adding reference footnotes, see Help:References.
Be sure to add the page you create into relevant categories. The icons template will automatically add the main categories to your page. You can always create a new category, but check first that it does not already exist with a slightly different name. Pop over to category:Content and browse your way through the different categories to gain an understanding of the general structure.
For ease of referencing, there is a short template for each Gemmell book which can be used to generate the ful title of the book with a link to the relevant page on the wiki. See below for the shortcodes for each book.