And what are some good books about Channel Islands history in general? I'm asking this question specifically because in a book I'm reading set on Guernsey, the main character's mother is described as being "chapel" while is father is said to be "church" and I don't know what that means.
The author means that his father is a member of the Church of England (the established church, in effect part of the state, and broadly equivalent doctrinally to the US Episcopalian church), while his mother belongs to a protestant non-conformist denomination, most likely the Methodists. The latter groups were "low church", emphasising personal faith and a direct connection with god over highly decorated churches, rich vestments, religious imagery and so on, and they had a less hierarchical clergy. All this was stressed by their choice to worship not in a specially built, architecturally distinctive, consecrated church, but in a plain and unadorned chapel that was often simply converted from an existing use.
The same distinctions were common outside the Channel Islands in the 19th and 20th centuries. Welsh identity in this period, for instance, depended heavily on whether one was church or chapel, the former being the religion of the middle and upper classes, particularly those with affiliations with the British state - white collar workers, mine owners and so on - and the latter being essentially the religion of the working classes, with services often conducted in Welsh. Marriages across this divide were not unheard of, but were certainly causes for comment.
Methodism arrived in the Channel Islands in the late 1780s when John Wesley, the founder of the movement, made a visit to Guernsey. By 1900 there were 32 Methodist chapels on the island and 7% of the population identified themselves as Methodists in the census of 1911 (by way of comparison, about twice as many people attended chapel as church in Wales at this time). The first Methodist chapel in the neighbouring island of Jersey was not opened until 1809.
Other nonconformist denominations active in the Channel Islands included the Baptists, the Presbyterians (Scottish, very low church), the Bible Christians (who merged with the Methodists in 1907) and the Quakers.
It would be fair to say that the Channel Islands do not have an outstandingly rich historiography, outside the numerous works covering the German occupation during World War II and a smaller group devoted to French and Norman influence on the islands' history. A recent popular history that places the islands in a slightly broader and more interesting context than usual is David Moore's The Other British Isles, which also covers Man, the Shetlands and the Orkney Islands, Anglesey, the Scilly Isles and the Isle of Wight.