A long time ago, a crafty friend gave me one of these, and ever since I've been making my own. I give them away as little mementos or thank yous, sometimes with writing inside and sometimes blank. I even taught my creative writing students how to make them. They're easy, simple, yet something a bit out of the ordinary.
Here are two stacks of them:

Some with velveteen paper covers:

Some with mulberry paper and fabric paper:

One, opened to the middle page:

An opened 5-page book (here's where you can see why they're called "Star Books"):

An opened 6-page book:

A close-up of the ribbon/bead closure:

Variations include:
* skipping the cover, gluing the end pages and using them as ornaments (great when made out of holiday paper/wrap, or colored vellum
* planning not to write anything in them and using patterned paper throughout
* gluing in small photos to fit the triangular sides of the pages
* some of my students have made them look like little mortarboards and have used them as graduation announcements
* make a pocket for a teeny tiny pen on the outside and they make cute "thought books" or "autograph books"
* write a list of why you love someone throughout the pages and give it to that person
Thank you for looking!

Edited to add: Due to all the interest, I made a tutorial here
http://www.craftster.org/forum/index.php?topic=197384.0.