Reddit reviews God Speaks Again: An Introduction to the Baha'i Faith

To be honest, if you're interested in learning about the Baha'i Faith in broad terms, the best way to begin would be with an introductory book. The classic of this genre is Esslemont's Baha'u'llah and the New Era; other good books include those by Smith, Momen, and Bowers (this last one is targeted specifically to a Christian audience).

Of the books you mentioned, The Hidden Words is probably the most accessible (and shortest!), and it's usually what I recommend to people who are interested in the Baha'i Faith. However, it's not always useful to look at the Baha'i Faith through the same lens as we may look at, say, Christianity or Islam, as having one or two "Holy books" that are central to all understanding. The Baha'i Faith is blessed with having many pieces of writing from the central figures of the Faith, and it's not possible to gain a full picture of the religion just by reading the four texts you mentioned.

Edit to add: The other excellent way to learn about the Baha'i Faith, which I heartily recommend, is to meet with some Baha'is from your area and talk with them. There are (relatively) a lot of Baha'is in Ontario (although I don't know where you are specifically), and there are usually ways to go about contacting them via the web.

The Kitab-I-Aqdas means The Most Holy Book, but I don't think it's fair to equate it with being the Baha'i Bible or Qur'an. It is one of literally hundreds of books and tablets which comprise the Writings of Baha'u'llah, the Prophet-Founder of the Baha'i Faith, all of which are sacred, all of which are equivalent in importance to the Bible for Christians/Qur'an for Muslims. It's also not the best reading for someone completely new to the Faith, as it is speaking to a Baha'i audience who is asking for laws, some of which might not be understood out of context.

On top of that, the Baha'i Faith has the Writings of the Bab (the Prophet-Founder of the Bab'i Faith, Predecessor to the Baha'i Faith) and 'Abdu'l-Baha (son of Baha'u'llah, authorized interpreter of the Writings of Baha'u'llah) which are given nearly equivalent weight. That brings the total volume of sacred Writings of the Baha'is to several orders of magnitude greater than that of most any other world religion. It can be difficult to know where to start, and overwhelming when someone heaps book after book after book upon you. We're not even getting into Shoghi Effendi or the Universal House of Justice yet.

God Speaks Again by Kenneth Bowers is a great starting point for someone who knows nothing.

Baha'u'llah and the New Era by J.E.Esslemont was the starting point for decades before this.

The Hidden Words by Baha'u'llah is my choice for a first read of the Holy Writings.

The Kitab-I-Iqan/Book of Certitude by Baha'u'llah is much heavier reading, but is the core of Baha'i Theology, if you want to dive into the deep end.

Thief in the Night by William Sears is my starting point for people who are intimately familiar with Christianity and the Bible.

My advice is to start with only one book, then move to others. Have fun!

Edited for grammar