The R.NET project provides a mechanism for communicating with R from a .NET application. This appears to be a promising way to create simple interfaces to some of the functionality of R.
There are the following book reviews on this website:
Book Review – Modern Applied Statistics with S by W. N. Venables and B. D. Ripley (Springer 2003)
Book Review – ggplot 2: Elegant Graphics for Data Analysis by Hadley Wickham (Springer 2009)
Book Review – Lattice: Multivariate Data Visualization with R by Deepayan Sarkar (Springer 2008)