There are a lot of good book suggestions but I'll toss out an alternative idea of buying "bad" kits. Kits that just take care of one task. Maybe its the RF gu

There are a lot of good book suggestions but I'll toss out an alternative idea of buying "bad" kits. Kits that just take care of one task. Maybe its the RF guts of a 30M ham radio receiver that barely technically works. Now you get to spend engineering effort on the somewhat simpler tasks of making a decent source of regulated noise free power, and build a decent AF amp strong enough to turn the headphones level audio into something driving a speaker using a couple transistors (or maybe an IC). And the input filtering isn't very good so you get to design a nice 10Mhz or so bandpass filter wide enough to let most of the receiver bandwidth thru but block enough interference signals especially AM radio transmitters. And now input signal levels are going to be low enough that a dedicated class A RF amp on the input might be a good idea to boost signals. Next thing you know you're going to be unhappy with the frequency stability of the VFO, so you either rig one of dozens of DDS VFO kits in its place or stabilize the free running VFO in the kit. Anyway the point is if you can regulate power and build amplifiers and filters but not quite up to the level of building a 30M radio receiver, then improving a bad kit would be a good plan. Likewise if your "wifi robot" you don't want is close source silo 100% maxed out no expansion possible it is quite useless. But if its got an IO pin or two and you want to learn how to light LEDs using resistors and maybe a transistor or two, you can use the wifi robot to handle the whole "how to turn it on and off" part while you focus on the source vs sink current limits and the excitement of inverting transistor driver circuits and the virtues of putting the LED in the collector or emitter circuit (assuming bipolar transistor) or the joys of trying to bias different types of switching FET transistors, oh its all a barrel of fun but by leveraging the unwanted "wifi robot" you can avoid some hassle. Also note that the "maker community" of java programmers learning to solder and the ham radio community of EEs learning to program java, never ever cross pollinate. However I live in both camps and the ham radio guys have decades of "learn you some electronics for greater good" general category of book. So if you're not having much luck with the maker style books there are literal decades of the ham radio branch "learn electronics" books. Check the ARRL to start.