I have found the following books helpful.
Artistic and Aesthetic Dimensions of Photography
Robert Adams, Beauty in Photography Essays in Defense of Traditional Values (Aperture, 1996)
Robert Adams, Why People Photograph: Selected Essays and Reviews (Aperture, 1994)
Philippe L. Gross and S.I. Shapiro, The Tao of Photography: Seeing Beyond Seeing (Ten Speed Press, 2001)
John Szarkowski, Looking at Photographs: 100 Pictures from the Collection of the Museum of Modern Art (Museum of Modern Art,  2009)
John Szarkowski, The Photographer’s Eye (Museum of Modern ARt,  2007)
Howard Zehr, The Little Book of Contemplative Photography: Seeing with Wonder, Respect, and Humility (Good Books, 2005)
Technical Skills and the Craft Aspects of Photography
Ernst Wildi, Master Composition Guide for Digital Photographers (Amherst Media, 2006)
John Hedgecoe, The New Manual of Photography: The Definitive Guide to Photography in Every Format (DK, 2003)
Special Kinds of Photography
John Shaw, Closeups in Nature: The Photographer’s Guide to Techniques in the Field (Amphoto, 1987)
Mark Gardner and Art Wolfe, Photography Outdoors: A Field Guide for Travel and Adventure Photography. 2nd Edition. (The Mountaineers Books, 2002)
Scott Kelby, The Photoshop Elements Book for Digital Photographers (New Riders)
Note: This work is frequently updated to match software updates of Photoshop Elements. Be sure to purchase the edition that is matched to your version of Photoshop Elements.