Step One - Determine the number of pagesI wanted it to be a short so I rolled a d8 and a d10, getting a 5 and a 9, so 59 pages long. I could have easily made it shorter or longer simply by manipulating the dice rolled. I felt 01 through 80 was a pretty good number for a small tome found by a first through second level party of adventurers.
Step Two - The beginning of the bookNo book jumps right into the spells, mages are an egotistical bunch of a-holes, so likely their writing would show signs of this as well. I made a quick decision to roll a d12 for each 'section' of the book, I figure 12 pages of a digest sized book is about right for a spell. So I roll for the first couple of sections (I threw together off the top of my head): Introduction, Author's Biography, and a discourse on Magic Theory. I think I drew on the horrible books in academia to get those, but you could throw in some other things like a dedication, history, maybe a family tree. Grab a book from your book shelf and flip through a couple and see what sort of things authors throw in the front of their books.
For each of these sections I rolled a d12, getting 5 pages of introduction, 3 pages of author biography (apparently this guy did not have much to say about himself), and 11 pages on magical theory. Already wasted 19 pages on crap my player will not care about but will make the book feel more 'real' or whole. Good job GM.
Step Three - Spells and suchNext we need to start getting the spells figured out. Now, one could just roll a d6 and say there are that many spells but that is boring. So I look for a random table I like and find none. I searched maybe ten minutes. Frustrated, I give up on a random table but instead find a list that I might be able to use:
If you are like me, you will see a pattern here. There are seven tables across there if you count the Cantrips. I decided I wanted Cantrips and only up to level 5 spells...boy that sounds like a damn d6 roll (1=Cantrip, 2=1st level, etc). This is perfect! I roll to determine the level, roll on the spell table, then roll my trusty d12 for page count. The first spell I get is Web, a simple spell that takes 11 pages! Hmmm, that seems like a lot of pages, so I dig into that "mages have egos" thing and decide the author rambles along and discusses the origin of the spell. He likes to write I guess.
I continue in this method, determine spell, determine page count, etc. Mentally, I sort of decided that 1 spell level should be about 1 or 2 pages so when the page count gets really high, I add a little flavor in to explain why a simple spell takes up so much space in the book. Doing this will add some depth to the book and make it unique, especially if you can add a little bit of the creator's character in there. If you wanted...you could even take this a step further and add a few sentence each spell. Maybe the author just loves his Phantom Steed spell and likes to create unicorns that shoot rainbows out it's butt. Maybe he likes to create camels because it reminds him of home. Maybe he has a quick concoction that helps remove the stickiness the Web spell leaves behind. Anyway, use as you like but I guarantee your players will dig any extra effort at thrusting some character into these entries.
I keep an eye on the page count until I get down to 9 pages left and as luck would have it, I roll the d12 again and get the result of the last spell taking 9 pages. Perfect.
Step Four - A silly nameI can't really help you much on this one. I just came up with a silly, ego-ish type name that sounded like some self-important mage might name his book.
My randomly generated magical tome
Here is the tome I created for my player. At some level I like to be more exacting in the spells I throw at my players to find, but then again I also like letting fate to decide what spells they get and then let the players be creative in figuring out ways to surprise me. Makes being the GM more fun. Below is the mysterious mage's tome that my player found.
“Delimar’s Exposition on Mystical Machinations”
59 pages total
5 pages of introduction, quite boring and due
3 pages of the author’s biography
11 pages of discussion on magical theory
11 pages, Web spell, a drawn out discussion on the origin of the spell
6 pages, Phantom Steed spell
12 pages, Friends cantrip, another long detailed story of the many uses of of the cantrip
2 pages, Identify spell
9 pages, Earthen Grasp spell