The rules are extremely simple and easy to grasp. And once you've grasped it, you'll never have to think twice about it.

Parentheses take precedence.

The first symbol is the operator (add, subtract, sum, multiply, etc.).

Everything else is operated on from left to right.

(+ 2 5 7)

2+5+7

It's also not a Clojure thing. It applies to all Lisps or related like Scheme.

All maths functions where it makes sense take arbitrarily many arguments. (+ 1 2 3) = 6. (< 1 2 3) = true. Everything in function position (directly after an opening paren) is either a function you want to apply or a macro you want to expand, except in a select few forms, such as binding forms and conditionals. The syntax of scheme is remarkably simple once you know the basics.

I have programmed python for about 20 years, and I still do stupid mistakes. I grooked all the r6rs scheme syntax in 20 minutes, except for (do ...) which somehow never sticks. It is also rarely used.

I have tried to evangelize scheme enough to know some people just don't like it, but for me it instantly clicked.

+ and = are pretty obvious but it can still be confusing. Take not=. Does (not= x y z) mean adjacent numbers are disequal (x≠y≠z, by analogy to + and =)? Or that no two numbers are equal? Or that at least two numbers are disequal? Different lisps pick different meanings.

Which lisps? I think I have only ever seen that in clojure (thinking it was a bad idea), and clojure seems scared of parentheses. (not (equal? x y z)) is clearer, but suffers from the same drawback as your question.

The problem I think is that not= returns true as long as any elements are non-equal, which means it is not analogous to +. I can't speak for clojure, but this is in line with all equality predicates in scheme, negated or not. A predicate that checked if any neighbours are not equal would in true scheme spirit probably be called not-any-neighbour-equal? :)