Logika Spiele is a German puzzle manufacturer. Probably their most interesting puzzle is the Cuboid in Cuboid (Schalenquader in German), an Assembly Puzzle.

The puzzle consists of 12 pieces plus the cuboid. The goal is to assemble the pieces around the cuboid in order to completely cover it. From the 12 pieces, you can divide them in two groups - one is for the eight corner pieces and the other is for the flat four pieces that go around the cuboid, one per face.

The jigsaw-like cut pieces and the puzzle concept sort of resembles the Happy Cube, especially the four flat pieces, which connect just about the same way. Assembling the puzzle is not that difficult, particularly if you take a trial and error approach, and with the low number of pieces, you'll probably solve it in less than 30 minutes. PuzzleMaster rates it at 8/10 (Demanding), but in this case I think it's probably more a 6 or 7.

Note that every piece is slightly different from each other, so you won't find two identical pieces. It's because of this that the systematic strategy has to be the best approach and direct way to solve it. More practical if you will. You start by placing the first corner piece on the cuboid and from the seven remaining ones, you see which one fits next. For every corner piece, there's three possible orientations, by rotating it around its vertex. 

The beginning is the hardest part, because you still have most pieces to place and a lot of possibilities. Not sure how many solutions are there, but probably not many or just only one, as there seems to be very few possible connections for a given piece. More over, I have solved it two times (weeks apart) and in both occasions the solution was exactly the same. 

There will be a few times when you think you're going well, but when you try to connect the fourth corner, no piece seems to fit. The solution in this case is to start over with a different corner piece. When you finally have the first four corners in place, you can start placing the flat pieces. Although you may have the corners in place, it's still possible that they're not solvable. Assuming you have a "winner combination", the next steps will be progressively easier, so when you reach to the last four corners, the solution is now certain and by then, you just have to fit them in their correct places.

Note: A customer on PuzzleMaster's product page comments that his puzzle doesn't stay together after assembled. All pieces on mine actually held on pretty good, except for one corner that keeps falling, but if I keep it in the upwards position it stays fine. I'm guessing the cut tolerances are different from puzzle to puzzle, so it's up to lady luck when you get yours. The puzzle comes with its own plastic container, though, so you can always put the pieces back inside.

Even though the concept is not the most original you ever saw, I can still recommend the Cuboid in Cuboid. It's probably not a big challenge for an experienced puzzler, but it's fun to solve and accessible to anyone.

Until very recently, PuzzleMaster had an easier version of this puzzle called "Cube in Cube", which basically just uses the eight corner pieces to assemble a cube, but it has been out of stock. Nevertheless, the Cuboid in Cuboid is still available.