There is the currently in-press book "Mathematical Foundations of Quantum Field and Perturbative String Theory" (n-cafe,nLab - note that the nLab is undergoing an upgrade at the moment, and may be unavailable) edited by Schreiber and Sati and published by in the AMS series Proceedings of Symposia in Pure Mathematics.
Links to arXiv copies of contributions are available at the above linked nLab page.

