Forerunners is one of the two extensive books published, to date, about the Strickler family in America. The other is Stricklers of Pennsylvania. I should be noted that both contain numerous errors. The foremost expert on Strickler family history, in my opinion, is Frank Duff. Frank is a poster here at Genforum. Richard Davis has also done extensive research on the Stricklers as part of his work on Mennonite families immigration.
Reprints of the Forerunners book are available from Iberian Publishing Co., 548 Cedar Creek Drive, Athens, Georgia 30605 1-800-394-8634 (orders only) , (706) 546-6740 fax
The Stricklers of Pennsylvania book has been out of print for many years, although, I recall Frank mentioned a company that may have reprinted it but I don't have that information handy. There are copies available to view from the Mormon church. You need to locate the Church of Latter Day Saints family research center nearest you and for a small fee you can order the book sent there from Salt Lake City for you to reference.
I also have much information on the families you mention and would be happy to share.