I'm interested in writing a book to introduce advanced physics to high-school level interested people. Sketch of the topics (hopefully covering all the examples that are important to everyday life and public debate.. should perhaps outline this, and the philosophy, in the first section, perhaps leaving history to brighten the later parts). Maybe the way to pull this off is to only loosely break it into these chapters, but strongly break it into small independent sections: that way mathematical detail can be contained, elsewhere it can be written for a most general possible audience, with loads of pictures (not just technical diagrams). It probably also makes it more fun to write, and useful to a broader crowd.
Physics is the reductionist science. A systematic evidence-based pursuit of knowledge, by the approach of deducing complex system behaviour from the dynamics of simpler individual components, and with emphasis on mathematics of the interactions rather than on cataloguing the complex systems.
Newtonian mechanics. This is always first, getting preliminaries out of the way (levers/gears/pulleys). Important topics: gyroscopes and Coriolis (i.e., unintuitive emergent stuff), waves (the foundations for understanding QM, such as Fourier, and can take examples of sound), impedence matching, fluids/flight. Vector calculus, trig., Lagrangians, conserved quantities. Surface tension (possibly need to break class. mechanics into simple and sophisticated techniques, or sections to showcase different mathematical concepts?).
Thermodynamics. The focus is statistics; gases are just an isolated example. Also cover heater efficiency, Carnot efficiency, stimulated emission, ..
QM. All just classical wave stuff really.
Electromagnetism: from the forces on static-charged pith-balls and magnetised iron-filings or compass needles. Self-consistency argument for Maxwell's equations. Leads to optics, electronics, relativity (Lorentz symmetry), and field theory (gauge symmetry).
Electronics (passives, relays to op amps and computers, meter/motor/generator, radio).
Optics. (This comes after QM.) Why stuff looks how it does.
Special relativity. Heuristic approach? Emc2. Paradox of FTL. Twins with focus on acceleration phase. Rotating disc.
Nuclear. This topic isn't tightly connected to the others, but is important (controversial) and poorly studied. Particle zoo.
General relativity. The idea is to explain basic differential geometry, and just give a fleeting example of an actual space-time. Tensors should have been introduced earlier.
QFT. Show field lagrangian of multiparticle QM. Fibre bundle stuff. Non-scalar stuff.