Some of the bookstores that I visit have been cutting back on the number of Gakken kits they carry, and the Shinjuku station east exit Kinokuniya had several of the earlier kits out in a display bin to get rid of them. And lately, the first 12 volumes or so have appreciated in price on Amazon (two are not even available on the auction sites now). Therefore, if I can find them in the store, I'll buy them on sight. That is, the kits that I don't already have from the first 12 volumes (numbers 2-5, 7 and 12). The rest I'll wait on until I can build my savings up. That's why I bought 3 kits in one week, rather than at the slower pace I'd promised myself that I'd follow.
Kit #9: Planetarium (2000 yen). Yes, I know, it's not a 400-seat auditorium with 3D animated fly-bys of the universe. But it's the next best thing - a little star projector you can put in your living room and stare at when you're bored. This kind of projector is very straight-forward - a light bulb inside a plastic box covered in a laminated sheet with pinholes representing the starfield as seen from the earth. I'm not sure, but I'm assuming that the starfield is accurate, and has about 10,000 stars in it. There's a calibrated ruler at the base that lets you change the display to match what you'd see in the sky in any given month. The kit also has an on-off switch, and runs on two AAs.
This is yet again one of those kits that has only 20 parts, and still takes forever to build. This time, it's because of the plastic sheets used for the box. There are four sheets, with pentagonal side panels. You have to fold the tabs and panel creases back and forth 2-3 times each to loosen the plastic up, then you tape the tabs together with double-sided tape. The plastic is stiff and hard to work with, and one tab was so brittle that it actually shattered like glass when I touched it. I didn't know exactly what the instructions were telling me to do, so I ended up putting half of my tape on the wrong side of the tabs, and any attempt to pull the tape off threatened to delaminate the starfield from the plastic sheets. Fortunately, there was enough extra tape in the kit to make up for my mistake. The final result is really cool, and lights up my living room with lots of little dots and splotches (just like it's shown on the cover of the mook). I like this kit. The finished product is also fairly large, taking up more shelf space when stored than a number of the other kits do.
Of course, there are the additional customizations that the editors suggest, such as cutting the base off to turn the projector into a ceiling lamp or star globe (to place into a stand like a regular earth globe); and to put paper mache on an umbrella to make a small projection screen for the kit. This last idea is pretty good, since the light dots look very clear on a screen at a distance of 4 feet, but are all fuzzy and diffused when on the wall and ceiling 12 feet away.
The mook discusses various planetariums, shows how the starfield had been created for the kit, and has lots of other unrelated articles about making a radio, a paper airplane and a robot; on collecting bugs; and there's a profile on a runner who has a prosthetic leg.
Kit #2: Spy Set (1680 yen). This is probably the weakest kit in the series, but has the most hard-science filled mook that I've seen so far. Technically, this is really a forensics kit, containing a polarized LED (the battery that comes with it is dead, though), fingerprint powder, and a couple small bottles of chemicals for identifying blood and other simple substances. The mook starts out with a murder mystery using the products in the kit to help solve the case. The bottles are small, and there's not a lot of reason to go around fingerprinting random stuff (I also don't have a big need for trying to find blood in the living room). Even if I did use the kit, the chemicals would run out quickly. So, in this sense, the kit has little more than a minor collector's value. Even so, there is a small amount of building to be done, in order to assemble the holder case (about 15 seconds worth).
The mook is the more impressive part. While it starts out with the murder mystery, it then goes into the actual science behind forensics, and how luminal works to make blood fluoresce under black light. There's also a section on low-cost DIY projects, such as how to make an arc lamp using a pencil lead, a Stirling engine with a piece of paper and two glasses of water, and how to use a rubber eraser to make copies of photos. There's a good section on how to collect various Japanese insects, an article on a man that makes musical instruments from straws, and a pair of 3-D glasses for looking at 3-D photos in the mook.
If you like the CSI TV shows, you'll like this kit. If you like building inexpensive science projects, you'll love this mook. It helps being able to read Japanese, but there's so many pictures and illustrations that the text almost becomes unnecessary.