Well, the blue circles are the gravity influence of the astronomical body. It makes your ship lose speed, so if it happens to you in the deep space, it usually means there is some undiscovered star or planet. Stars influence area is really huge. Just today, thanks to this mechanics, i found an red dwarf i was looking for (Draconis B, it was 260000ls from Draconis A!). Draconis A orbit showed me the direction, i was already losing hope to find it (only intermediate scanner onboard) i was going already at 800c and my speed started to drop, so i knew its somewhere here.
I dont know about the source of material explaining it, sorry. But you are right, it is quite faster to hit the top speed, go very close to a planet that your target station orbits, go around it (or beside, as long as you are in the planets gravity influence) and lose the speed close to the planet. This way you skip the long breaking, you can literally go from very high SC speed to almost 5 Mms. After 200ls of constant accelerating you can get as close as 1 ls close to the target station, its awesome. Also, great if you want to avoid interdictions, as deccelerating is the best opportunity for a hostile to catch and interdict you.
So, you were right to think theres a faster route than direct one

. Just try not to hit the planet, the emergency SC stop can damage your ship.