The publisher looks pretty credible.
Arvol Looking Horse is a recognized medicine man from Cheyenne River (pretty sure it's Cheyenne River...someone correct me if I'm wrong please) The "White Buffalo Teachings" is not necessarily a book as it was an accompaniment of Arvol's World Peace and Prayer Day and according to the publisher...recently republished.
Wilma Mankiller was the former principal Chief of the Cherokee Nation of Oklahoma and IMHO one of the most profound leaders ever produced on American soil in modern times woman or man/Native or non-Native.
Can't comment on the others as I don't know enough about them.
One of the publishers, Harvey Arden, has a long history of working with indigenous people and lectures at many credible institutions on the works you've listed. I haven't read them however, and cannot comment much further, however I do like what he says about himself on his bio page on his own website.
http://www.harveysplace.net/bio.html"Regarding why I, a white guy, am so involved in the indigenous world, I subscribe to the philosophy expressed in this statement by Australian Aboriginal Elder Lilla Watson:
"If you've come here to help me, you're wasting your time.
But if you've come because your liberation is bound up with mine,
then let us work together.""
Just keep in mind...they are books and not a substitute for actual life lessons, however he does seem to chronicle some amazing people and those stories alone are inspiring.
Superdog