simple, simplistic

Simple or simple means uncomplicated; easy to understand--
Our students would benefit from regular practice with simple math problems.
The directions are plain and simple; anyone can follow them.

Simple may also mean plain or unadorned--
She wore a simple dress of pale blue linen.
We'd like a simple sign; one with just the house numbers on it.

Simplistic or simplistic describes reducing something to nonsense, as a philosophical outlook, or in an effort to make it easier to understand--
His reasoning is simplistic; there's more to the problem than can be understood at a glance.
His argument is simplistic; he sees things in terms of black and white, with no shades of gray.

Now that you know that, you can say--
"We asked for a text with simple explanations, but these are simplistic; the students won't learn anything but how to repeat them."