There is no prohibition against reading LDS history by non-LDS sources. An Ensign (official LDS publication) article by Elder Steven E. Snow (LDS Church Historian) here:
lds.org/new-era/2013/06/balancing-church-history?lang=eng includes this quote…
*Certainly, the world has changed in the last generation or two. The Internet has put all kinds of information at our fingertips—good, bad, truthful, untruthful—including information on Church history. You can read a great deal about our history, but it’s important to read about it and understand it in context. The difficulty with some information online is that it’s out of context and you don’t really see the whole picture.
Information that tries to embarrass the Church is generally very subjective and unfair. We should seek sources that more objectively describe our beliefs and our history. Some websites are very mean-spirited and can be sensational in how they present the information.
Look for sources by recognized and respected historians, whether they’re members of the Church or not.*
I hope this helps…