A fictionalized retelling of the life of Jesus, with a focus on the Passion, is a nice idea. To that effect, the Thoenes portray life in ancient Rome and, later, in Jerusalem, in a credible manner, although not quite as successfully as in the previous two books of the Jerusalem Chronicles.
Behold the Man, however, turns out to be a disappointment. Characters are two-dimensional - either irritatingly good and suffering such as Claudia, Marcus and Jono, or unbelievably evil, such as Vara and, especially, Pilates, who the reader expects to be a complex, unpredictable ruler. There are major holes in the story: the reason for Herodias' animosity towards John the Baptizer, for example, which is clearly presented in the Gospels of Mark and Matthew, remains unexplained in the book. Longinus, who Christian tradition believes to have pierced Jesus' side with a lance after his death, as narrated in the Gospel of John, never does so - making the informed reader wonder why he was named liked that in the first place. Worst of all, the trial, death and resurrection of Jesus, which should be at the climax of the book, come to a hasty end as if the writers badly needed to meet an editor's deadline. Religious undertones prevail across the story in a form that would hardly be expected at the time considering it took several centuries for the events surrounding Jesus' life to sink in and mature. This makes the story little appealing to the non-believer: a more objective approach would have been far more effective.
If you want to read the screenplay for an old-fashioned biblical movie from the 50's, look no further. If you'd rather read modern historical fiction, try something else.