Agilent has developed a very nice qPCR-based method for quantifying NGS libraries. This application gives researchers a useful and fast tool for their NGS workflows. At the Science Direct website, you can find a paper describing the technique and other benefits of using it. For example, the authors “find that qPCR quantification may allow improvements to current NGS workflows, including reducing the amount of library DNA required, increasing the accuracy in quantifying amplifiable DNA, and avoiding amplification bias by reducing or eliminating the need to amplify DNA before sequencing.”
The relevant product page on the Agilent Genomics website can be found here.