When expressing satisfaction, admiration or approval in Italian, it is perfectly acceptable to use overtly positive expressions such as Che bello! (How wonderful!), Fantastico! (Fantastic!) or Meraviglioso! (Marvellous!).
However, in some cases, you may want to express a positive judgement using a litote (a negative, often ironic understatement that expresses a positive meaning). One frequently used litote in Italian is Mica male!
Although it literally translates as Not bad (at all)!, the underlying meaning is actually Very good! or Excellent! You can use it on its own or precede it with the verb essere (to be).
Com’è la loro nuova canzone? – Non è mica male, sai!
What’s their new song like? – It’s not bad at all, you know!
The phrase is made up of two components: mica (adverb meaning ‘not, at all, in the least‘) + male (bad). It can function both as a response to a question as in the first example, or as part of a comment as in the second example below.
Mica male questo film, temevo peggio!
This film isn’t half bad, I was worried it would be worse!
A possible synonym for mica male is niente male, with niente meaning nothing / no / not any.
Cosa pensi della mostra? – Niente male!
What do you think of the exhibition? – Not bad!