It is all in what you want out of the publication and you are the best judge of that before you buy it. If all you are looking for are more pictures of custom 1:6th figure bashes, then I would say no, it is not worth 38 bucks plus shipping. OSW Has a lot of great work by some very talented individuals and most (if you PM them) will help you with your figure.
If you are looking for more information on how things are done/made/sculpted/created/etc. then perhaps it is worth the money. It also depends on your skill level in the hobby. If you are fairly adapt at building and making your own equipment, uniforms and weapons, then it will be of very little use to you. If you are also really good at embellishing a figures body to make it more posable then, no the book is of little utility.
However, there is information in the book on 1:1 equipment so you can see how it really looks and is used. There are tutorials and How to's but, they are in Japanese. The book also provides pictorial information (since it is in Japanese) to stimulate your thinking on making figures. There is always a theme with each volume (British is the theme in 3) that makes it a bit interesting. Generally the figures in the magazine are from a host of customizers so you get to look at different styles. As this hobby has developed so has the level of detail, functionality, and quality of the products we used to customize our figures which provides us the capability to bash some truly outstanding figures.
I purchased SpecFigure 1 and 2. Each edition of the book has provided good information and has helped me grow and developed my skills. By the time Book 3 came out I am now much better at bashing and will to take more risk at augmenting or modifying figures so, the information in the book is not as unique but, it is still informative. There is still good-to-know information in the book. However, forums, such as OSW, also provide a path for obtaining information and to get assistance.
I like SpecFigure3 for the quality and detail of the pictures, information on 1:1 equipment and uniforms, and for the bits of information it provides on customizing. However, the is only my opinion. True, it is not of the grand stand nature that Specfigure 1 and 2 was. But, it is still good info. The big question is still what are you hoping the magazine will provide you or how it will help you? If I knew what that question was, I could give you a better answer.
Hope that helps!