These are some books written by members of the meetup.

Learning R

Richard Cotton

Parallel R

Q. Ethan McCallum

Machine Learning for Hackers

Drew Conway & John Myles White

Analyzing the Analyzers

Harlan Harris, Sean Patrick Murphy & Marck Vaisman

Applied Predictive Modeling

Max Kuhn & Kjell Johnson

Testing R Code

Richard Cotton

Testing R Code

Richard Cotton

Bad Data

Q. Ethan McCallum

Text Mining with R

Julia Silge & David Robinson

R for Everyone

Jared P. Lander

Bayesian Data Analysis

Andrew Gelman, John B. Carlin, Hal S. Stern, David B. Dunson, Aki Vehtari & Donald B. Rubin

Machine Learning for Email

Drew Conway & John Myles White

Doing Data Science

Cathy O'Neil and Rachel Schutt

A Quantitative Tour of the Social Sciences

Andrew Gelman & Jeronimo Cortina

Teaching Statistics: A Bag of Tricks

Andrew Gelman & Deborah Nolan