Phone books are a great addition to your compost pile when prepared properly. The thin pages work great as a mulch-like layer in composting. Add them dry if your compost pile needs less moisture, or wet if it is drying out too much; it's up to you. They can be treated much like old newspaper. The important thing when composting an old phone book is to be sure to remove any non-paper components, like metal staples or plastic inserts.
Get the old phone book ready to compost. Check through it for any non-organic materials, like metal or plastic. Sometimes phone books have magnets, plastic door hangers or other non-compostable things. Remove these items and discard.
Cut off the directory cover, using sharp scissors to get as close to the binding as possible. If you aren't sure if the cover is paper or plastic, better to toss it than put it in your compost.
Pull the phone book apart into small sections of pages. Pull these sections off the binding rather than trying to cut the binding off the phone book. Try to rip the pages as close to the binding as you can to get the most use out of the old telephone directory. When they are all off, discard the binding.
Cut or shred the directory pages. You want to make an easily biodegradable "bird's nest" of paper shreds so that the paper will have maximum air circulation in the compost pile rather than sitting in a lump. The narrower the strips, the better; you may want to use a paper shredder if you have one.
If needed, wet the shredded phone book pages. This will help them degrade faster in the compost pile. However, if your compost is already very wet, you can use the dry shreds to lighten up the pile quite effectively.
Mix the paper shreds into the pile. Use the opportunity to turn the compost, mixing in the paper with the existing materials so that it gets the most exposure to the composting process and has plenty of air and moisture.