Do you want a theory book or do you want course lesson material?.
If you are looking for course / lesson material I liked Faber's Adult Piano Adventures. The first book was very helpful as was the Christmas book. The second book did not quite "blow the wind up my skirt" but I plugged thru it. These will get you going. The Christams book was great fun.
After this series you should be ready for the Frederick Harris "Celebration Series" which will really get you into serious study.
A good read which you should be able to get at your library is Charles Rosen's "Piano Notes".
If you want theory material I can recommend that as well but I would just start off with Faber and have some fun. Faber does include basic theory. Their web site follows but you can buy it thru Patti Music as well as several of the other online dealers. www.fjhmusic.com www.frederickharrismusic.com