Sufis believe that at the core of all religions lies the same truth and that God is the only reality behind all forms of existence.
Wills’s book is What Jesus Meant, reviewed here by Jon Meacham:
Jesus was neither a politician nor a prelate, and this book’s most significant contribution may lie in its reminder that faith is far too important to be considered solely, or even mainly, in political or ecclesiastical terms. Skeptical of the papacy and of many Catholic traditions, Wills convincingly shows that Jesus was a radical whose essential message to love one another totally and unconditionally is fundamentally at odds with the impulses of those living in a fallen world. Jesus left sundry examples of how one should live not for power but for the poor, not for fame but for forgiveness. But it was God’s own unconditional love for this fallen world of ours that led him to do the unimaginable to save it: he sacrificed his own son. The Passion makes the greatest sense for readers if it is seen as the culmination and ultimate expression of what Jesus had been saying and doing in his few years of public life. “Father, forgive them,” the dying Jesus says from the cross; the Resurrection on the third day, Wills says, bears out the words in the Song of Songs “love is as strong as death.”
I haven’t read the book, but the interview is worth a listen on its own merits.