Does the fact that all of the information in the novel may not be percise take away from validity of the boook as a memoir that depicts that brutal war in Sierra Leone?

Yes, I have heard about the inconsistencies. This question is really up to you. I'm not an expert on Sierra Leone but I do know both sides used child soldiers and evidence of what boys like Ishmael went through is well documented. Perhaps some of the facts were embellished or misinterpreted but if one turns on any news cast, they will see the same thing. So no, the inconsistencies do not bother me. The boy obviously went through hell and back. Failing to be accurate about the cocaine mixture that was pumped through his veins is of little consequence. Remember that this is my opinion. It is your interpretation that counts here. Read the facts and think it over. I would like to hear what you think.