The real prerequisite for machine learning isn't math, it's data analysis - SHARP SIGHT LABS

These are two excellent books on machine learning (AKA, statistical learning; AKA, model building). If we're talking about entry level data scientists to intermediate level data scientists, I'd estimate that they spend less than 5% of their time actually doing mathematics. Even if you use "off the shelf" tools like R's caret and Python's scikit-learn – tools that do much of the hard math for you – you won't be able to make these tools work without a solid understanding of exploratory data analysis and data visualization. While this figure is about data science in general, it also applies to machine learning specifically: when you're building machine learning models, 80% of your time will be spent getting data, exploring it, cleaning it, and analyzing results (using data visualization).