He developed his own curriculum,[3] which his parents supplemented by requiring him to read four single-page biographies of successful people every day, which were collected from the pages of Investor's Business Daily.

[2][4][5] Using the WYSIWYG site-building tool Homestead, Spartz founded MuggleNet, a Harry Potter news website and forum, in 1999, at the age of twelve.

[7] The book remained on the New York Times Children's Bestseller List for six months, peaking in the number two position and selling 350,000 copies.

[10] In 2009, Emerson Spartz and Ben Schoen wrote another book, MuggleNet.com's Harry Potter Should Have Died: Controversial Views From The #1 Fan Site.

[11] By 2007, Spartz was receiving a six-figure income for running MuggleNet and had recruited six paid and 120 volunteer staff to the site.

[6][12][13][14] In 2015, he stated, "As I became less motivated by my passion for the books, I got obsessed with the entrepreneurial side of [MuggleNet], the game of maximizing patterns and seeing how big my reach could get.