The quality of the components could be better, resistor colour bands are poor, more emphasis should be put on the description that a lot of components/equipment required to do everything are not included.
The book is not without faults, and should have been proof read. Words missing out of sentences, and showing an inverting operational amplifier as a non-inverting operational amplifier could cause confusion.
The book also lacked technical depth, and should not have included poor coverage of microcontrollers. Also having an illustration showing the keyboard of a Pi connected to the micro SD slot shows lack of quality. The "advanced" chapters should have been removed, they are very shallow in detail and add nothing to the book. I would have preferred more technical detail in the previous chapters a section on using operational amplifiers to increase signal from sensors would have been appreciated, including non-linear sensors. Additions to the electronics kit to provide more practical circuits, that had shallow coverage in the book, with no actual circuits, would have been better. The section on EMI was far from detailed. Fortunately, I had other kits so I could extend the circuits that were hinted at in the book to actual experiments. I expected better from Elektor, this kit has made me think a lot more about buying anything else from you.