These two approaches should help you:

Use the Google Books "Search in this book" feature on the bottom right (after you've opened the book at Google) Type in the names/words you want.

Look at the indexes at the end of the book -- Index I (Christian Names of Clapps) starts on page 399 and Index II (Names of Persons Who Have Married Into the Clapp Family) starts on page 414.

I suggest doing these things online rather than trying to print out over 400 pages!