I would consider both to be outdated, interesting reads to learn how people used to think about poker but not a priority.

If your friend is nerdy enough (not scared by multiplication and the word percentage) https://www.amazon.com/No-Limit-Hold-em-Advanced-Players/dp/1880685590/ref=sr_1_2?s=books&ie=UTF8&qid=1550768137&sr=1-2&keywords=janda#reader_B071W92Y8Q this is probably what I'd buy him, it's leagues above most books. Don't be fooled by the 80s style cover, Janda's material is based on game theory which is the "modern" way of thinking about poker. The reason it got a 4 instead of a 4.5 is probably because math allergic people won't be able to read it

If not https://www.amazon.com/Exploitative-Play-Live-Poker-Manipulate-ebook/dp/B07KPKNGM6/ref=pd_sim_351_4/135-8225113-7074201?_encoding=UTF8&pd_rd_i=B07KPKNGM6&pd_rd_r=e26db4d5-35f9-11e9-8361-31a05a5f3960&pd_rd_w=TudBf&pd_rd_wg=QzYrh&pf_rd_p=90485860-83e9-4fd9-b838-b28a9b7fda30&pf_rd_r=64DN7ZTD95NBH4719356&psc=1&refRID=64DN7ZTD95NBH4719356#reader_B07KPKNGM6 this one seems good based on the table of contents and sample.

The second one is a safer bet for sure btw, you need to be really into poker and have studied basic stuff to enjoy the first one