I will look for a book with a hard front and back cover.  If the book has 100 pages, I will glue them together in 10s. I use a variety of different glues.  Nothing real special.  Sometimes Yes!, Golden Mediums and Polymers, or sometimes Elmers mixed with something else.  After gluing, I stick a bunch of paperclips on it.  When it is almost dry, I take them off and start smoothing it down and working with it.  This will give me 10 solid pages to work against.  In the case of the smaller books, I traced out 20 "pages" on 140 lb paper.  I then proceeded to decorate, paint, collage etc. those pages that were traced out.  It is easier if you don't cut them out until they are all done, since they are so small.  Keep in mind which pages you want to put together, color scheme, subject etc.  After they are all dry, and completed, I cut them out and glue them to the book pages.  When that's dry, I add some more paint and touch ups.
There is a lot of labor for me doing altered books.  I like for them to look a certain way, so I am not into timing myself at all.  It is pleasure for me more than work. 
Altered books seem to be getting more and more popular.  They are such unique creations.  So much more than a single collage or painting.  I have described one way to make them.  I am sure every artist has their own method.
Jeanett's work can be bought at Esty
and you can see more of her wok on her blog
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Working on a whole altered book might seem a bit daunting, so try this neat idea from Jeanette Janson, and make your own personal themed altered book to keep for yourself.
Using a small book 3ins x 4ins divided into 6 sections these are treated like pages and are beautifully collaged. Jeanette's theme for this book is 'Faith',  and she covered the book with hammered copper and made a copper clasp to keep it closed.