I'll make one more suggestion that fits what you are looking for from an unexpected direction. See pic.
>where religion plays a central part, but sanctimonious and cartoonish presentations of it do not.
That's not exactly correct. Greene does include such presentations, yet he is lampooning it when he does. At the least, it is clear his sympathies stand against such aspects found in religion.
Also, Greene could be described as a part time punch-clock Catholic. This characterization is understandable as seen by people who are more traditionally religious in their thinking, and outlook. For them, a book like Siddhartha can be a profound, even life changing, experience.
There are others who find Greene to be more serious, sincere, and dedicated to religion than those of a more traditional outlook are easily able to perceive. In this case, something like Siddhartha makes not even the least impression on them, spiritual or otherwise.
It should be obvious I fall into the latter camp.