What is more, books you can take with you and read them whenever you want, and for those who love reading they are always a good company.

those 是指示代词"那些"，在这里指代前文提到的"热爱阅读的人"。 who 是关系代词，引导定语从句，指代前面的 those（那些人），在从句中作主语。 those who 是一个固定搭配，意思是"那些...的人"，用于引出特定群体。