I've come across a number of references to the gospels/gospel of late.
Muslims
Muslims seem to think that The Gospel is a book given to Yeshua as the Quran was claimed to be 'given' to Muhammad.
The misunderstanding sets in, it would seem from Christian's casual use of the word 'gospel' to apply to the texts that convey it.
We do it often with a rule book. Typically we would ask that someone passes the rules to them, say, during a game of Scrabble. What they mean, of course is the rule book.
So Mo. thought the gospel was a book. That would make sense for one who had a reputation as an uncritical fountain of stories he had heard but not understood.
As a result Muslims regard the gospels according to the named four as somehow a corruption of what God 'sent down' with Yeshua (or his deprecating Quranic doppelganger 'Issa')
But the 'gospel' the 'good news' (euangelion) which means 'good news' or 'glad tidings'. The Quran is simply unaware of this.
So the four gospel accounts (which we also shorthand to 'gospels') are four depictions of the work of Yeshua as the foundation of the good news. Fundamentally it is death and resurrection and defeat of death opening the way to fellowship with God through a new life that is the good news.
It is worth noting that some scholars consider the book that Mo. was referring to was the Syriac peshitta, a collection of a number of the books that now make up the Bible
Moderns
Some detractors of the Gospel, and indeed some followers of Christ I've heard refer to the gospel accounts as 'biographies of Jesus' (sic).
They are not. They are concerned not about his life per se, but about his mission as the Son of Man, Messiah.
They link Yeshua's actions with the OT and show him as Messiah by his actions and words. God is the 'good author' in this way: Yeshua shows us, as well as tells us. Just telling is easy, anyone can do it. Muhammad, for example.
In modern parlance, the gospel accounts are more like an 'after action' mission report. They sum up the mission, the actions taken, the ground covered, the people and conflicts encountered and dealt with and the final result (it is finished).
Far more focused than a mere biography. The separate accounts are four 'mission reports' by four of Yeshua's band.