it is not a simple sentence
A simple sentence consists of a subject, a verb, an object and adverbials. It is also called a clause.
A complex sentence is made up of several of these simple sentences or clauses and can therefore contain several verbs.
Your sentence:
Quote:Reading is something most of us take for granted.
can be better understood as
Quote:Reading is something THAT most of us take for granted.
"THAT most of us take for granted" is called a relative clause and it relates to the "something" of the main clause.
We can also write your complex sentence as two simple sentences:
1. Reading is something.
2. Most of us take it for granted.