These are some books written by members of the meetup.

A Computational Approach to Statistical Learning

Bryan Lewis and Michael Kane

ggplot2: Elegant Graphics for Data Analysis (Use R!)

Hadley Wickham

R for Data Science: Import, Tidy, Transform, Visualize, and Model Data

Testing R Code

Richard Cotton

Machine Learning for Hackers

Drew Conway & John Myles White

Red State, Blue State, Rich State, Poor State

Andrew Gelman

Advanced R: Second Edition

Analyzing the Analyzers

Harlan Harris, Sean Patrick Murphy & Marck Vaisman

Python for Data Analysis

Wes McKinney

Teaching Statistics: A Bag of Tricks

Andrew Gelman & Deborah Nolan

Machine Learning for Email

Forecasting: principles and practice

Rob Hyndman

Applied Predictive Modeling

Max Kuhn & Kjell Johnson

R for Everyone

Jared P. Lander

Feature Engineering and Selection: A Practical Approach for Predictive Models

Max Kuhn

Learning R

Data Analysis Using Regression and Multilevel/Hierarchical Models

Andrew Gelman & Jennifer Hill

Bandit Algorithms for Website Optimization

John Myles White

Pandas for Everyone: Python Data Analysis

Daniel Y. Chen

Text Mining with R

Julia Silge & David Robinson

R Cookbook: Proven Recipes for Data Analysis, Statistics, and Graphics

JD Long

Data Analysis with R - Second Edition: A comprehensive guide to manipulating, analyzing, and visualizing data in R

Tony Fischetti

Data Science at the Command Line

Jeroen Janssens

Bad Data

Q. Ethan McCallum

R Packages: Organize, Test, Document, and Share Your Code

Hadley Wichkam

Learning R: A Step-by-Step Function Guide to Data Analysis

A Quantitative Tour of the Social Sciences

Andrew Gelman & Jeronimo Cortina

Bayesian Data Analysis

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

Deep Learning with R

JJ Allaire

Getting Started with D3

Mike Dewar

Parallel R

Introduction to Empirical Bayes: Examples from Baseball Statistics

David Robinson

Doing Data Science

Cathy O'Neil and Rachel Schutt

Service-Oriented Design with Ruby and Rails

Paul Dix