This hugely impressive work of poetry, although based on Malory's epic "Morte d'Arthur" and other early books, does not, in truth shed much light on the "Arthurian" Age, but it is immensely revealing about the Victorian era.
In these poems, Arthur is an English gentleman rather than a Dark Age Celtic warlord, or even a medieval ruler. But this approach serves to illuminate what was best about the Victorians, decency, courage, self belief. It is fashionable to knock the society of England in the Nineteenth Century as being repressive, dictatorial, even hypocritical. Tennyson's poetry, along with the work of authors like Kipling and Robert Louis Stevenson show, largely, a positive side to the time.
My only regret with "The Idylls" is that the shorter poem by Tennyson on the subject of Arthurian romance, the cracking "Lady of Shallot" is not included in this book.