Gerard
First, i admit i have a bias toward LGB.
Second, i am a luddite and run DC track power. Very limited digital.
Third, i tend to prioritize simplicity and ease of execution, labor and maintenance. ie I am a lazy lout.
Ive been running a garden layout, of some type, since 1995. I started with an LGB starter set and some extras track and cars. soon , grew to larger US style 4 axel equipment as well.
I recommend 2 books by LGB , "Track planning and Technical Guide", or, "Explore the World of LGB" .
These two are very similar, the second being an update and edited version of the First.
I also like "Garden Railroading: Getting Started in the Hobby". very useful and more focused on construction
Why do i like the old LGB books?
i make the assumption that it is likely you may use LGB/Marklin products as a beginner. They are still most widely available, new and used, and, imho, despite shortcoming in scale and fidelity, are highly reliable and top quality. This is the one product I recommend to anyone who has little or no model train background or modeling skills, because they are simply, truly, ready to run. They are also far from artful in many cases, compared to fine scale. Otoh, they will not frustrate the owner by temperamental operation or tracking. They are robust, and weatherproof.
The books i mention are designed to explain simple electronics (analog), layouts, building roadbeds, simple garden plantings, and are an easy to digest and comprehensive overview. IMHO, they are immensely fun to read and peruse.
They focus entirely on LGB products, and the track plans are ....a bit antiquated, as they are very much oriented to sectional track construction, electro mechanical automated train operation and somewhat crowded layout designs in many cases. OTOH, they are very well done and reliable should you find what you like. I find, that your layout will be dictated by your space and its unique factors, thus, many suggested layouts wont quite be right for you. It's still a source to learn about possibilities.
That being said, i have used these for years, and i find the methods still reliable, whether laying track on lawn, in a shallow trench with ballast, or a raised roadbed. I think they are a good place to start for the basics. I have found with re-reading each, there are subtle details and technical information which are superb.
They do not offer any info on digital operations.
FIWI, Explore is newer, and last time i looked, less costly than the earlier Track Plaining edition. OTOH, i find both worthwhile, the Track Planning version has some great prototype information and photos omitted from Explore. I believe both were printed in English and German editions.
I recommend these as , i believe these are as basic and introduction friendly as i have seen. Lots of photos and diagrams. I have many other garden railroad books. These are still my most read.
i would also recommend internet sites, such as Elmassian.com, sidestreetbannerworks (find and read Mark Horovitzs philosophy on garden trains and aesthetics) and others. Many of these have excellent, straightforward tips and methodology for building.
I would part saying, simply buy a starter set, some extra track and 2-3 switches and play with it, indoors or in the garden. You will learn a lot by simply "doing" a railroad. I am not a "master plan" type usually, as can be overwhelmed by possibilities.
By dipping in with a modest investment in a starter set, some extra track, you can immediately enjoy a railroad, learn as you set things up and wire switches, etc., and see how it performs, i.e. grades, outdoors, train lengths,etc.
Most here, me included, do not use the 4ft diameter curves, as they are tight, unrealistic, and will not favor longer engines and stock.
IMHo, it can have its place and be useful, notwithstanding its limitations.
I did use this small radius curve for several years before i had a permanent layout, and, unequivocally, i was delighted to have trains to run, even if toy like.
Otoh, it does work best with short, toy like cars, short trains, and the stainz type 0-4-0 locos, and doesn't take up much room. IMHO, it's a convenient way to start, even if you abandon it entirely in a year or so.
Or, like a patient, thoughtful and prudent adult, you can plan your right of way, and buy only the needed appropriate track...........LOL.