I think you have to ask yourself why he picked out this book. You can even try asking him how he heard about it, if you can do it in a curious non-judgmental way.
If you think he chose it because he wanted the team to improve or grow in this area and the title sounded like a good fit, you can probably be more honest with your criticism, especially if you can offer other theories or strategies and recommended the sources you learned them from. In this case, I think he'd care more that his book triggered these discussions than whether it was strictly any good.
But if you think he has read and enjoyed this book himself, or that he saw it advertised on LinkedIn and thought it would be a nice manager thing to get it for everyone, I think you should keep your comments more positive. Tell him about any parts that you did think were good, point out the topics that you're most interested in researching further, tell him about any ideas for the team that were triggered while reading, etc.
I think you have to ask yourself why he picked out this book. You can even try asking him how he heard about it, if you can do it in a curious non-judgmental way.
If you think he chose it because he wanted the team to improve or grow in this area and the title sounded like a good fit, you can probably be more honest with your criticism, especially if you can offer other theories or strategies and recommended the sources you learned them from. In this case, I think he'd care more that his book triggered these discussions than whether it was strictly any good.
But if you think he has read and enjoyed this book himself, or that he saw it advertised on LinkedIn and thought it would be a nice manager thing to get it for everyone, I think you should keep your comments more positive. Tell him about any parts that you did think were good, point out the topics that you're most interested in researching further, tell him about any ideas for the team that were triggered while reading, etc.