This book was such a surprise. I loved it. Justin Richards is very hit or miss for me, and this particular Who novel just did everything right. This was my first 5th Doctor novel and it was so, so good. Tegan's character was toned down to the point where she was tolerable. Since Nyssa was indisposed for almost the whole novel, another part-time companion stepped in- a butler from 1896. He took the time-traveling in stride and was capable and intelligent and I'm almost sorry he didn't stay on in the Tardis. Speaking of time travel, there's A LOT of it here. The Tardis is used often in the novel, which isn't usually the case. Typically it's used as a vehicle to start the story, but isn't used as a plot device like it is here. I loved the Egyptian lore, the excavation, and the use of the mummy robots. They didn't feel shoehorned in or contrived. The way the story was told took a little getting used to, as you're constantly shifted back and forth in time to relay the events. It's a little violent, so heads up on that- at least half a dozen or so people die rather grotesquely.
Davison's Doctor was spot on and he acted exactly as I would expect him to. He was calm, intelligent, a little scatter-brained and observant. His mannerisms were exactly right, to the point where this really could have been a 6 part or so arc of the show.
This novel fits in a short time after Adric was lost, so watching Earthshock and having that frame of reference might help, but I'd really recommend watching Tom Baker's story arc The Pyramids of Mars before you dive into this one. It gives you background on Sutekh, the Osirians and the robot mummies seen here.
Sands of Time was just FUN. The story was constantly moving and pieces of the puzzle were being uncovered right up until the end. I'd highly recommend this one if you're a fan of classic Who.