Check out their page http://www.gao.gov

You can find a list of some of their available material at
Special Publications: Evaluation Research and Methodology
http://www.gao.gov/special.pubs/erm.html

Order one copy of any book for free.  Order from the order page, http://www.gao.gov/cgi-bin/ordtab.pl

- Designing Evaluations. PEMD-10.1.4. May 1991. Guidance. 78 pp.  http://www.gao.gov/docdblite/summary.php?rptno=PEMD-10.1.4&accno=144040   or pdf version here  http://archive.gao.gov/t2pbat7/144040.pdf    and here  http://www.gao.gov/special.pubs/pe1014.pdf    

- Case Study Evaluations PEMD-10.1.9, November 1990   http://www.gao.gov/special.pubs/pe1019.pdf   

- The Evaluation Synthesis PEMD-10.1.2, March 1992   http://www.gao.gov/special.pubs/pe1012.pdf 

- Performance Measurement and Evaluation: Definitions and Relationships. GAO-05-739SP, May 2005.   http://www.gao.gov/cgi-bin/getrpt?GAO-05-739SP      

- Quantitative Data Analysis: An Introduction. PEMD-10.1.11. June 1992. Guidance. 110 pp   http://www.gao.gov/special.pubs/pe10111.pdf 

- Using Structured Interviewing Techniques. PEMD-10.1.5. July 1991. Guidance. 92 pp.   http://www.gao.gov/special.pubs/pe1015.pdf 
    abstract here  http://www.gao.gov/docdblite/summary.php?rptno=PEMD-10.1.5 

A couple of other books at the GAO website not listed there are these.

- Developing and Using Questionnaires PEMD-10.1.7 October 1993 238 pp.   http://archive.gao.gov/t2pbat4/150366.pdf   

- Using Statistical Sampling, PEMD-10.1.6   http://archive.gao.gov/t2pbat6/146859.pdf    

- Content Analysis: A Methodology for Structuring and Analyzing Written Material. PEMD-10.3.1. September 1, 1996. Guidance. 57 pp.   http://archive.gao.gov/f0102/157490.pdf   
abstract here   http://www.gao.gov/docdblite/summary.php?rptno=PEMD-10.3.1