After that I recommend a book on Chess opening. Which one? There are so many and you are the only one who knows what openings best peaks your interest. Therefore you may have to get a number of books until one of them really works best for you.
Reading all these books is training in itself simply helping you to become more proficient in understanding chess books. The more you take the time to read the better you get. Build your own chess library and take the time to read that book again and you will be amazed with better clear understanding of that book.
Have fun
I want to recommend to low rating players, who are new to chess or have less experience in chess like me, the book "How to Reassess Your Chess" by IM Silman (I don't know if he is a GM now). There are four reasons
1. It is cheap! $23 for a 658 pages book is cheap to me. I know it well because I am a victim of a Vampire named "college textbook".
2. It covers all topics related to Strategy that beginners should know well.
3. I learn how to analyze my game thanks to this book. This means that I can learn better and improve faster.
4. I have an idea of what to LOOK for and how to THINK in chess. Like, if you throw me a situation, I can at least tell you "hey I think this piece is badly placed". Better than "I have no idea man, I am lost!"
https://www.amazon.com/How-Reassess-Your-Chess-Imbalances/dp/1890085138