I’d say that each of these doctors’ works are geared towards different levels of prayer: St. Therese’s for the beginner, St. Teresa’s for the experienced and St. John’s for the proficient at prayer.
Having said that, I think that a person can be at the same time beginner, experienced and proficient at prayer, so by all means there’s much to be gained from reading all of them. However, a beginner is not that much experienced and very little proficient, so it’s more likely that St. Therese will make sense more often at first than St. John. Of course, St. Teresa is sort of in-between, so she’s perhaps more approachable by all.
Yet, St. Teresa was a very busy woman and wrote her works between founding convents, often on the road. So, unlike St. John, her style is very informal and convoluted, sometimes addressing specific needs of her daughters intermingled with theological points. It’s no surprise, because she didn’t expect that her writings would have the wide audience that they did, she was writing to her Carmelite daughters. In this sense, her autobiographical “Life” is easier to read and has many pearls of wisdom and teaching about prayer and conversion.
St. Therese, on the other hand, is better known for her autobiography, “Story of a Soul”, but Carmel really shines through her letters. If one ever wondered why she’s patron of missions, one could not understand that by reading just “Story of a Soul”, but by reading her letters. All of her works are excellent in demonstrating a life enriched by St. Teresa and St. John.
St. John is the best author, having had extensive education as a religious, although he came from a very humble origin. His works have a very practical focus, even when he uses poetic language, and he uses it often. At the same time he’s also the one that speaks most about Gos’s Love, almost like the Psalmist. However, I can’t say which of his works is more approachable, for I’ve just started reading him.
There are other Carmelites here and they’re much more knowledgeable than me so I’m sure that they’ll cover my many gaps above.
I think that this can be put in different terms:
*]St. Therese calls us to start praying for a fuller conversion of our hearts.
*]St. Teresa calls us to pray for endurance of conversion.
*]St. John calls us to pray for abandoning ourselves to God.[/LIST]Again, I think that all need all of the above always, only the degree of one or another that changes, and even so it doesn’t change linearly only in one way, because we always need conversion of heart and to persist in it in this side of Heaven.