How Specifically the Control Unit (CU) Works
As a software developer, you understand and apply abstraction and encapsulation. A control unit (CU) is just an abstraction for handling sequential execution and making decisions. You know that Javascript is completely emulated by software and has a software CU. The Javascript CU
steps through an array of instructions (i.e., your program) and executes them. The Javascript CU has a concept of "current instruction", which is just an index into the array of instructions. Equivalently, an electrical CU has an instruction pointer register (a bunch of flip-flops) which stores the address of the next instruction. The Javascript CU makes decisions based on variables. An electronic CU uses a fixed number of registers for its variables.

Register values change with each clock cycle. Everyday computers are synchronous and everything changes with the clock: memory is fetched, the instruction pointer is changed, etc. To make a decision, the CU chooses what the next address should be and that address is loaded into the instruction pointer for the next clock cycle. The electronic mechanism of choice can be as simple as a single NAND gate. And now we're down at the electronic level. You can do a lot with NAND gates. Interestingly, you can build a whole computer out of them.

An example of a simple CU is an alarm clock. One register is for the alarm time. One register is a counter for the current time. The clock increments the current time. We use logic gates to compare the registers. An AND gate is &amp;&amp;. An OR gate is ||. An inverter is "!". Just write the logic equation yourself and you have basically wired the comparison. When the comparison is 1, the alarm rings. This very simple CU had to make a decision and the needed electronics exactly matched what you might program.

The fascinating thing about software is that everything can be turned into hardware. A neural net cat be software or hardware. At this point your own curiosity should be your guide. Feel free to search for any concept you can think and search "circuit for X". Try this now. Look for "circuit for comparing". You don't need a book.

NOTE: Although NAND is computationally complete, for clarity I've introduced AND gates, OR gates and inverters. You can also use NOR gates. When I learned this, it unlocked everything.