As of 2015, several books about HO track layouts are in print. Atlas Railroad Modeling Company, Inc.'s website carries its own line of books, including "The Beginner's Guide to HO Model Railroading," currently priced at about $8 and "HO Layouts for Every Space" for about $9.
ModelTrainStuff.com carries books from a wider selection of publishers, such as Model Railroader's "101 Track Plans for Model Railroaders," which includes plans for all scales, including HO, currently priced at about $16.
Magazines provide another print source for HO track layouts. Model Railroader offers a subscription that includes its printed periodical as well as online access to track layouts that appear in the publication. Free online resources are also abundant. Kato Precision Railroad Models offers a collection of detailed HO track layout instructions as free, downloadable PDF files.