Long comparatives (бћлее-comparatives) are somewhat bookish and are avoided in conversational Russian.
To avoid a long comparative in the predicate position, use the short comparative.
To avoid the long comparative in attributive position (i.e. modifying a noun), use the по-comparative: add the prefix по- to a short comparative form:
bookish: Ї купќл бћлее интерљсную кнќгу. I bought a more interesting book.
normal: Ї купќл кнќгу поинтерљснее. (Same meaning.)
Sometimes the longer form isn't used at all, but the по- comparative is very common:
  Ї хочџ кнќгу побћльше. I want a larger book.
Јтот словђрь похџже. This dictionary is not as good (as the other one).
Мљнее 'less' works like бћлее 'more'. You can avoid it by using не такћй.
bookish: Јто мљнее интерљсная кнќга. That's a less interesting book.
normal: Јто кнќга не такђя интерљсная. That book isn't so interesting.
Note this common idiomatic expression:
  — ТІ приготћвил домђшнее задђние
— Бћлее или мљнее.
"Have you done your homework?"
"Yes, more or less."