Tell me about it! I ordered “Spoken Taiwanese”, and it is completely worthless. It has no grammatical explanations whatsoever, nor any repetition whatsoever. I think it will be valuable once I’ve made my way through the Maryknoll series as further practice, but beyond it isn’t a good starter for learning the language. Maryknoll is the only way to go, but I have read that “Spoken Amoy Hokkien” is a far better starter than “Spoken Taiwanese”, but the accent is quite different from any spoken in Taiwan.
It seems like missionairies in general make good language material. Someone on here, a previous Mormon if I remember correctly, says the Mormon books/tapes are excellent. I know another Mormon who lived in Taiwan for two years and his Mandarin was excellent. It makes sense. Missionairies really try to teach their students the language; many companies are just looking to package whatever crap they can in order to sell it and make a buck.