"tel" means "such"; "un tel (noun)" means "such a (noun)". Or "une telle (noun)" if the noun is feminine.
Can this be an intensifier or is only for the situation of "things of that nature"? For instance, "un tel idiot" as a way of stressing how idiotic someone is?
There are several answers possible here. "lisez" and "lisons" are correct too.
'Ne lisons pas un tel livre' = 'Let's not read such a book'.
So, not correct.
It is grammatical English, it's just that nobody says it precisely like that because it sounds too stilted nowadays; it evokes Shakespearean times. Imagine yourself at a conservative book club. Somebody suggests "How about '50 Shades of Grey'?", and half the room replies "Let's not and say we did".
"Let's <do something>" is fairly common usage, as is "Let's not <do something>". Let's not go out tonight. Let's read 50 books this year!