Rest, Ortner, Ilming , Verlag Militaria , Austria , 2002 (English)

Perhaps not German Pickelhaube but this is a major labor of love. HUGE. More than 1400 pictures and the only explanation in English of the K.u.K. Army. It is all here.  Referenced, backed up, researched and organized.  If you want Austrian stuff this is the book. They printed it in German also. Two thumbs up. I use it as research not reading. My goodness these guys actually understand the morass of Austrian uniforms.