This is the only acceptable Lao course in English which I could find.
The explanation of the tones, which are something new for English speakers, is adequate, and the script is well explained. For both, some things are missing. With some extra work, and the internet, these were not hard to figure out. The "g" is not voiced as the book says, but you can figure that out from the CD's also.
The CD's are extremely useful because there are many errors in the tone marks in the book.
The book's biggest flaw is that the vocabulary is not representative.
The number of words you learn in the book must be about 650 or so. Unfortunately, the authors do not seem to have used a frequency list. In the 650 words there are complete lists of animal names, body parts, professions, and elaborate time telling. This leaves very little space for basic vocabulary. After studying the course, I was still missing too many words for simple conversation.
The book seems to be written a bit in a hurry, or the authors did not keep track of what they have done before. There are doubles in the vocabulary, while some new words pop up in the texts. An example: on page 170 there is a special note to one of the sentences, that "bpaandai" means "not so much", while the expression has already been listed in the vocabulary on page 127, and been used in the sentences section on page 45.
I found later that Lamvieng Inthamone's course is a much more serious Lao course. Maybe time for a translation into English ?