^I agree. Khan is being evasive. Saying "I am reading the manual all about your ship" is more inflamatory than "I'm reading manuals about starships" The second sounds more general and less incriminating. Spock knew it was a mistake and Khan knew it also, but he didn't want to loose that access. I think hanging on to the specific syntax of a line of dialogue without it's context is illogical.
I agree wholeheartedly, but
no one less than the captain had granted Khan access to the starship manual of the Enterprise
, so there was no need for Khan to hide the fact he was studying the manual of the Enterprise
Quite on the contrary, his "confession" that he didn't limit his studies to the one of the Enterprise
but also studied other manuals could have arised suspicion...