If, from your reading of The Fountainhead you are intrigued by the ideas which are specifically discussed in The Virtue of Selfishness then go read it definitely. In my case, after being blown away by The Fountainhead, I read most of her non-fiction works together side by side, never completing anyone in one go, just choosing which topic I wanted to read more about from anything Ayn Rand wrote herself. But still one book stood out for me at that time: Philosophy: Who Needs It. Also, a good supplementary go-to source I found was the Ayn Rand Lexicon, the whole book is readable online under the same name.
Personally, If I were you, I would not touch anything that has any excerpts from her novels other than The Fountainhead. All the best!!!!!!
