Smear: NKT sells only Geshe Kelsang's books
Truth: Tharpa Publications does largely sell only Geshe Kelsang's books, but there is nothing wrong with this. For the Kadampa practitioner, these books contain all the teachings required to attain enlightenment, and they form the basis of all NKT study programs.
Each book contains commentary to a root text by Buddha Shakyamuni, Je Tsongkhapa, or another great realized Buddhist master. For example, Ocean of Nectar contains the translation of Chandrakirti's entire root text Guide to the Middle Way, Universal Compassion is a commentary to Geshe Chekhawa's Training the Mind in Seven Points, and Eight Steps to Happiness is a commentary to Geshe Langri Tangpa's Eight Verses of Training the Mind.
Many of the books are structured like Dharma scripture because they are based on the outlines that come from Je Tsongkhapa's texts and they contain a huge number of quotations from Buddhist scriptures and references to other Buddhist texts. In short, they are authentic and authoritative teachings of the Buddha and many other respected Buddhist Masters; they are neither a new creation nor the exclusive work of Geshe Kelsang.
Tharpa Publications also sells a translation of Shantideva's Guide to the Bodhisattva's Way of Life; and there is nothing to preclude Tharpa Publications from producing other stand-alone long translations in the future.
By selling only Geshe Kelsang's books, Tharpa Publications is not suggesting that these are the only valid Buddhist texts or that Geshe Kelsang is the only valid Buddhist teacher. There are many Dharma books in this world and many wonderful teachers. If an NKT student or anyone else wants to read books by other teachers, they can easily obtain them from any good book store.
For all the criticism of the NKT and Geshe Kelsang, there is rarely any criticism of Geshe Kelsang's books, which are highly praised throughout the Buddhist world as being authoritative and authentic. These books are the Dharma at the heart of the study programs, and the study programs are at the heart of the NKT, which indicates that the NKT is a valid and respectable Buddhist tradition.
Although the NKT has a non-sectarian attitude toward Dharma books, sadly Geshe Kelsang's books are not sold by some general Buddhist outlets or even bookstores because they are following the sectarian view and politics of the Dalai Lama. No one is asking them why they don't sell Geshe Kelsang's books even though they are highly respected; they only ask why Tharpa Publications does not sell books by other authors.