Our family uses this book every week day to pray for the world. This book leads you to pray for 100 different countries or people groups. It is simple, uncomplicated, and a very practical prayer guide. I think it's great for children, but I think adults can also read and use it. It is not as detailed as the Operation World guide, but it is still very educational and give you tips to pray for each highlighted country or people group.
This is what it practically looks like for our family (I tried to highlight in blue on the picture): We usually pray longer on Mondays, Tuesdays, and Thursdays--with how it fits our life schedule this year. We read the fast facts and what to pray each of those days and then one of the paragraphs each of those days. On Wednesdays and Fridays, we look at "what to praise and pray for" and only pray. So, in praying for one country or people group, I think we will be using this resource for the next 2 years. I highly recommend it!