Head-over-heels in love with the adventure, intrigue and bonhomie of archaeology, Hugh Thomson (The White Rock) explore Moches, Chavin, Nasca and other ancient civilizations of Peru. His tale is bracketed by an account of his discoveries with Gary Ziegler at Llactapata, a newly excavated observatory barely two miles from Machu Picchu.  (PRU76, $16.95)