Regarding the book by Daniel Boyarin, The Jewish Gospels, see The Divinity of Jesus in Early Judaism « Ratio Christi- Apologetics At The Ohio State University.
John the Baptist’s preaching is a window into what at least some Jews believed about the coming messianic age. For the most part, there was a consistent belief that the Lord himself would intervene in some way in history and render judgment. Israel’s enemies will be destroyed and the nation gathered in a restored kingdom in the land promised to Abraham. Both Matthew and Luke describe John as declaring that this judgment would be made by a messiah, who is coming soon.
The Temple was therefore central to the life of the “common Jew.” As N. T. Wright puts it, “At the heart of Jewish national life, for better or worse, stood the Temple”
Philo indicates the primary purpose for going to the synagogue was to study scripture.