To be fair, religion does not emerge very well in this excellent novel. The two main characters who are used by Bronte to comment on religion are the Reverend Brocklehurst and her own cousin, St. John. From her very first meeting with Brocklehurst, it is clear that he is associated with severity and hypocrisy, as the following quotation from Chapter Four makes clear:
I looked up at--a black pillar!--such, at least, appeared to me, at first sight, the straight, narrow, sable-clad shape standing erect on the rug: the grim face at the top was like a carved mask, placed above the shaft by way of capital.
Note the use of the metaphor a "black pillar" to describe Mr. Brocklehurst, and also the inference of hypocrisy in comparing his face to a mask. As his later treatment of Jane and actions show, Mr. Brocklehurst is a hypocrite who lets his own daughters curl their hair whilst insisting the girls at Lowood have their hair straight, even going as far as having one girl's hair cut off because she has natural curls.
It is interesting that Mr. Brocklehurst is described repeatedly with the colour "black." St. John is described as being "white" or "ivory," yet it is important not to let this denotation of colour suggest a completely positive approach of his religion. St. John is a man obsessed with his goal of becoming a missionary, as this quote reveals:
A missionary I resolved to be. From that moment my state of mind changed; the fetters dissolved and dropped from every faculty, leaving nothing of bondage but its galling soreness... I know I shall overcome, because I have vowed that I will overcome--and I leave Europe for the East.
If Brocklehurst's religious fault was his hypocrisy, St. John's fault is his zeal and obsession, which drives him to manipulate Jane and propose to her even though he does not love her romantically. St. John presents a very different view of religion that is governed by zeal and obsession alone, and where reason controls all. However, his attitude to religion is much more positive than Mr. Brocklehurst's, and critics have pointed out that the novel ends with St. John's words, suggesting a respect that the author has for such zeal.