The Versus guides were very nice. The ones Prima have been releasing for the 4th generation have been very nice quality too. It's just...FireRed/LeafGreen was the anomaly. Here's a comparison of what they have:
Prima FireRed/LeafGreen Guide:
Introduction
How to use this book
Pokémon types
Type chart (no other context)
Where to find Pokémon (grass, fishing, surfing, evolution)
How Pokémon evolve (trading, stones)
(back of guide)
TMs
HMs
Berries
Advertisements
Prima Ruby/Sapphire Guide
Introduction
How to use this book
What's different in Generation III
Battle menu
Types of targeting in double battles
Status conditions
Type chart and how they work
Other ways to increase damage (STAB, critical hits, items, weather)
Physical vs. Special
TMs and HMs that can be used in the overworld
Natures and a Nature chart
Where to find Pokémon (grass, surfing, fishing, diving, Rock Smash, swarms, breeding)
Types of Poké Balls
How Pokémon evolve (level-up, preventing level-up evolution, stones, trading, Happiness, special cases--Wurmple, Feebas, Shedinja)
Breeding (passing down Egg Moves, passing down IVs, what will hatch, Egg Groups, Egg Group chart, hatching Eggs)
(back of guide)
Move chart for battle (name, type, base power, accuracy, PP, range in double battles, contact or not, TM/HM if any, additional effects)
TMs and HMs
Move chart for Contests (name, type, appeal points, counter points, additional effects)
Contest combos
Item chart for those that get used up
Berry chart
Hold Item chart
Key Item chart
Mail chart
Poké Ball chart
Secret Base Decorations
Wild Pokémon with Hold Items
I've seen the 4th generation guides too, and they get into stuff like EV-training and more tips, largely those introduced in that generation. I relaly hope Elizabeth Hollinger continues to write Pokémon guides, because it's pretty clear she genuinely enjoys Pokémon, knows a considerable amount of it, and can explain it in a way anyone can understand.
I say this because the 5th generation, while it hasn't been any less beginner-friendly than before, has introduced so many new abilities and the new moves are generally for experts only, so if Prima makes a guide for Black/White she should do it.
By the way, the Prima guides ARE the official guides--starting with Diamond/Pearl, Nintendo now commissions Prima to write guides instead of Nintendo Power. I don't know if Hollinger continues to write them though. Can anyone check?