Online educational startup Knewton has raised $6 million in Series B financing from Bessemer Venture Partners and returning investors, which include VC firms Accel Partners and First Round Capital as well as several angel investors who had participated in the $2.5 million Series A round from May 2008, such as LinkedIn founder and CEO Reid Hoffman and Zenbe co-founder Peter Stern . The company says it will use the extra capital to better serve both the enterprise market (where it says demand for its adaptive learning engine is growing) and end consumers with its online test preparation services. Read an excerpt from Erick's earlier review after the jump, or head straight to the post from late last year to learn more about Knewton.