This is what i do, but i also dont have close to 
as many books as you have, but im working at it. 
^_^x I print out about 8 pics of my cels on a 
piece of paper with enough room to write a few 
facts about it next to it. They are usually in 
the order they are kept in my books, but not 
always. One of the facts i write next to the 
image is the book its in and page number for 
easy reference, along with scene and sequence 
number, ect. I keep all the printed cels pics in 
a clear folder next to my books and look at it 
before i try and figure out which book a certain 
cel is in. If something gets moved i cross out 
the old and write in the new. Its sort of my 
catalog for my cels. I hope this helps or gives 
you a better idea. Well anyway, i wish you the 
best in your cel collecting. 
Happy Lainning!
rayd
ps. the comment before about the cels dividing 
was funny, i wish they did that in my collection 
but i guess i havent reached critical mass yet.