Durnan Publishing's motto can be summarized in three words: Easy, Simple and Practical, hence ESP.
Can anyone point out any grammatical mistake in above sentence?
There are no grammatical mistakes as such, but it is not a partcularly good sentence.
I would say that Durnan's publishing motto is 'Easy, Simple, Practical'; its publishing philosophy can be summarised as 'Easy, Simple, Practical'.
Note that 'Easy, Simple and Practical' is made up of four words.