I was very impressed by this book. Having owned/played/GM'ed many, many modern games over the years, I found this to be a refreshing take on an old system and a relatively under-used genre. I have been very impressed by many of the games coming from Small Niche Games and I plan to continue following them to see what other role playing gems they put out in the future. The support for this game has already been tremendous, with a prolific number of adventures already available in a short amount of time.
The system is still OD&D, but the class structure isn't overwhelming. One of the things I love about OWB is that it uses the grandfather of all fantasy rpg's without being one. You won't find a hint of elves, magic users or dragons in this book. It's a very good take on a modern (by that I mean guns and tanks, not swords and horses) historical rpg. It was nice that they tipped their hat toward weird science and Nazis in space, but the game isn't inherently set up around anything surreal.
At first I was a little dismayed reading through the stats, weapons and combat. I kept thinking, "What about Hit Dice? Why is the weapon damage so flat-rate? Why just d6's?" Of course I was expecting more of a D20 Modern layout to all these things. Then, after I read through the introductory scenario, it all hit me. This isn't an 80's movie action take on WW2. It's extremely realistic. You have 1d6 hit points. Most weapons do at least 1d6 damage. If you run out in the open yelling, "Shoot me Shoot me Shoot me!" Someone will likely quite lethally oblige you. It's a refreshing change of pace. In fairness, you can still play in heroic mode and bump up the Hit Dice, etc.
I also really like the fact that there is no advancement beyond Level 5. It totally makes sense given the war itself didn't last that long. It also helps keep the combat realistic and somewhat gritty. Your character is part of the war effort, not winning the war single-handedly in both theaters of operation, and not coming out at the end with millions of gold coins, his own castle, and hundreds of followers.
My only real recommendations for improving the game are an expanded list of equipment and vehicles, by primary country and dates of deployment. (US, USSR, Germany, Great Britain, France, Italy, and Japan) There don't need to be volumous notes on everything, just enough to give each country's gear a somewhat realistic feel beyond "Rifle, Large." or "Tank, Medium." Also, it might have been a good idea to focus a little more on languages. The language barrier for Americans in Europe and Japan should probably come up on a regular basis in game. A little more detail overall on the timeline at the beginning of the book or in the GM section would have been helpful for a younger crowd or one with less familiarity with history. This is one of the only games I've ever seen where some outside research is fun and helpful in running and even playing the game. My players are getting brief history lessons with their rpg time Bwah ha-ha! and that's awesome.
I was also balked slightly when the hardcover was made available the day after my softcover arrived in the mail. If only I had waited... Oh well. I just have to take really good care of this softcover until I can find a friend to give it to and order the hardcover for me.