First Time Post here. As someone who actually does have experience in NT studies, I agree with @swamidass and @dga471. Alter’s book is not something that would convince any fair minded historian. There are a number of glaring problems with it that should pop out to anymore informed reviewer. For instance, the use of rabbinic and other Jewish texts is outdated and uncritical. It is widely held that they don’t accurately reflect 1st century Jewish legal practice (among other things). You cannot read them at face value. Most scholars would disagree with his use of them as in the case of Jesus’s trial and evaluation of Pilate’s character. See The Trial and Crucifixion of Jesus: Texts and Commentary by Chapman and Schnabel for an actual scholarly overview of the subject.
Alter also uses older sources that have been superseded by new scholarship and fringe sources that a less discerning audience might not be aware of- like when arguing against the bystanders at Jesus’ cross. Maurice Casey was a good scholar on some things, but his work on John is is close to reverse fundamentalism. Likewise, Corley is a part of the Westar Institute which is basically the Jesus Seminar redux. Nowadays people have a much more positive opinion on the historical character of John. Take his citation of Barrett’s supposed refutation. If you actually read the text from Josephus Barrett cites, it’s about getting permission to take people off crosses, not merely approaching them. His understanding of Jesus being crucified because of maxime maiestatis causa damnatorum (high treason) is unlikely- see Craig Evans, John Welch, John Granger Cook, etc. There were a variety lesser charges that fell under maiestatis like laesa maiestas or seditio. For Barret’s argument to work he needs to have Jesus charged with maxime maiestatis causa damnatorum, but Pilate explicitly finds no fault with Jesus in the gospels and doesn’t see him as a political threat. That’s why a number of scholars who favor the lesser charges like John Welch, Craig Evans, John Granger Cook, Jürgen Moltmann, etc.