I've seen these around the internet and decided to try making my own. This is my first tutorial and I forgot to take pictures while making it so please bear with me.
And I apologize for any over explaining. Just trying to make up for lack of pictures.
So first things first, lets dismantle that book. I reccommend leaving endpapers at the front and back there, they'll come in handy later.
Just past the endpapers you can cut through the glue that holds the pages together. Do this in the front and back so you've got the 'meat'of the book out.
For now just set the pages aside. To make it hangable by the spine I cut a slit on either side in the joint. I did it towards both the top and bottom to make it hang more evenly.
Now you can go ahead and rig your string however it pleases you so your mobile will hang.
Now for the fun stuff. So the pages are still held together with the book glue so you have to pull the pages off. I only did a few at a time to try and keep them from ripping. Some of them stayed together in pairs or groups of three which made for some cool loops.
Tip: The fullness of your mobile depends on how many pages you use. I only needed about half of mine.
Now time for the fun (and time consuming) part! Start glueing your loops.
Put your glue on one of the long edges of the paper and fold it over but make sure there's no crease. This is also where those paperclips come in handy. Clip/pin both sides and leave it to dry.
Tip: It's best to leave a bit of a 'tail' so it'll be easier to put the loops together later.
When your glue's dry you can stand the loops on end and arrange them how you see fit. Glue them together to get your design then glue the mass of pages to the cover.
Give it a good bit to dry and then hang it from the ceiling :)
If you have any questions I'll be more than happy to answer them. Other than that, Enjoy!