Both can be just take on face value as scholars, Ehrman more prolific writing books for the general public. Ehrman's books often have standard themes, explaining how one should read sources, the due care we should have regarding them, the secular means of studying them, details regarding gnostic writings and orthodox responses to such "heresies," and so forth. Thus, there overlap and a book about a particular thing (here a recently re-discovered Gnostic themed gospel where Judas is a good guy) has a lot of background not specifically about that.
The background is helpful though and this small volume (around two hundred pages with notes) covers a lot of ground, including the story on how the document was obtained, what we know of Judas from various sources and discussion of what could be read of the damaged gospel itself. The Wikipedia entry covers a lot of ground and you can read the actual translation -- seven pages long -- which for whatever reason (perhaps copyright issues or it wasn't completed in time) is not included here. A longer account that goes into how the gospel was found and includes some discussion of the actual text is The Lost Gospel: The Quest for the Gospel of Judas Iscariot, Ehrman providing an introduction.
Ehrman for obvious reasons was excited about the discovery, in part because it provides a different perspective. The gospel appears to have been originally written mid-second century, fairly early as gnostics go, this Coptic copy from the late-third century. It covers the last week before the "betrayal," more a neutral "handing over," since here Jesus wants him to do it, since it is necessary to release his "true self" from the prison of his body -- the basic gnostic idea. The gospel tosses in some fairly standard (though the nuances depends on the work) detail of the creation of the universe with various mystic aspects and the overall concept that the "god" most praise isn't the REAL ultimate being. It ends with handing Jesus over -- no death or resurrection -- some gnostic accounts that do portray the death have someone else on the cross.
The four canonical gospels make it a negative thing (for somewhat different reasons -- he does it for money, because the devil made him do it, for some unclear reason), but the basic idea makes sense, doesn't it? Jesus was destined to die and rise from the dead, though I guess he could have surrendered himself to the authorities. Matthew suggests it went all by how the scriptures predicted and John basically has Jesus some fully divine presence that knows everything coming anyway. Luke says a devil made him do it, which fits the themes of that work and the gospels in general -- Jesus is here to guide us to the kingdom of heaven, a savior who fights the evil that took over this world. Thus, the significant importance, including the apostles, of casting out demons.
We obviously don't know why Judas did it and if it was for money ("Judas," as the author notes, eventually being a sort of symbol of "Jews" as a whole -- money grubbing betrayers of Jesus/Christians), that would be bad. The author provides his own theory, but it's based on limited information, really merely guesswork. If he did it out of ignorance of Jesus' true role, this shouldn't be too surprising -- a lot of people, including over and over again the apostles were pretty clueless. Mark has a centurion declare Jesus' true identity and women (worthless witnesses under current thought) find the empty tomb. The first would be last, the last first. On some level, why not Judas?
Overall an interesting account that covers such ground. One notable thing is that the gospel has Jesus "laughing" at various points, something that he doesn't seem to do in the canonical gospels. I discussed a book that suggests the importance of humor for well-rounded Christians here. and that author suggests the gospels do have some comic elements. Remains interesting -- and Ehrman's works help us look at the sources in a way that makes us think in such ways -- how Jesus laughing (perhaps in a dismissive way) is a notable thing. Jesus is understood by Christians generally speaking to be both human and divine. Humans -- at least the well balanced types -- do laugh from time to time.
Elaine Pagels co-wrote a book on the same subject a bit later. Ehrman cites both in his book. Some reviews suggest they had somewhat different interpretations than Ehrman, but I have not read her account yet.