Training essentials for Ultrarunning by Jason Koop - https://www.amazon.com/dp/B09MYVR8P6
Although written with Ultra Running in mind, it is a gold mine for endurance/speed training and racing in general. Highly recommend his podcast too: https://www.jasonkoop.com/podcast
Although written with Ultra Running in mind, it is a gold mine for endurance/speed training and racing in general. Highly recommend his podcast too: https://www.jasonkoop.com/podcast