I bought life-time subscription to Agora a while ago at a hefty discount at the suggestion of a friend. Most of their newsletters are worthless but I will make an exception for Chris Mayer's 100 baggers. He thinks like a value investor and shares good insights. I do my own research - but his newsletter is a good source of investment ideas and articles on investing.
At $49 a year, it is worth the price, imo. I will stay away from everything else.
I haven't read his book.