I ordered Lapshun's "PLay b4!" and Konikowski's "b4. Theory and Practice" as well
I own all 3 books. You just have to watch out for what each one says about certain things. For example, Lapshun over-estimates the Sokolsky Gambit - 1.b4 e5 2.Bb2 f6 3.e4 (First 8 of the 11 games in the chapter). Hansen doesn't even cover it. The theory and practice book covers it but acknowledges that it is basically "equal at best" and indirectly saying that Black is probably for preference.
Another untrustable line Lapshun covers is one with an early f4 - I think it is game 18, but not looking at the book at the moment. Even they say declining with 3...d6 (I think it is 1.b4 e5 2.Bb2 Bxb4 3.f4 (Just take on e5) gives Black the advantage. They do a lot of this. They throw in games because they are cute, but in reality useless. If memory serves me right, I think this was the one where White got the Rook on h8 and Black "promoted" to Queen with hxg1, of course recaptured, I believe by the king.
The b4 Theory and practice is a complete coverage book, but can be confusing because they often refer you back to other games from previous side notes, and some may view as a database dump of lines as there is less prose. If you need a line for Black, that is the place to look.
Now keep in mind, complete coverage is complete coverage of what was known in 2009. 4.c3 in the Exchange Variation was a fairly new phenomenon and everyone played 4.c4 or 4.Nf3, both of which got full chapters, along with 2...f6, 2...d6, and 2...e4, all got a chapter each. Lapshun's is a repertoire book with some added "cute" stuff. Ignore the cute stuff, which off the top of my head I believe is just games 1 through 8 and 18, and you basically have a repertoire for White.
So here is how I see the 3 books:
Hansen - Some of the more modern ideas. I use his gambit line against the out-flank attack. This one is legit as you are not weakening the White King to do it. In Lapshun's gambits, they all are f4-based. This one is 1.b4 c6 2.Bb2 Qb6 3.a3 a5 4.Nc3! (This is covered as a sideline, he also covers 4.c4) axb4 5.axb4 Rxa1 6.Qxa1 (the point of the pawn sac) Qxb4 7.Na4 f6 (only move, and many amateurs don't find it, it is to prevent 9.Be5) 8.Bc3 Qd6 9.Nb6 Qc7 etc. Moves like Na8, Qa7, Ba5, etc, all come into consideration. I also think his coverage and the theory and practice coverage of the German Defense (1...d5/2...Qd6) is better than Lapshun's.
Lapshun's book is good if you can weed out the garbage (games 1-8 and 18) and also consider that some legitimate lines by Black are left out - like in the German Defense, particularly Black's 4th move.
The theory and practice book is the most dense, the hardest to follow, will require the most work, but is the most complete based on 2009 standards. The assessments are the most accurate, and what is covered really has not changed. They just don't cover some of the newer ideas, like Carlsen's 4.c3 in the Exchange Variation or the 4.Nc3 gambit in the Outflank Attack.
So I would read Hansen's and Lapshun's first, but keep in mind you are basically wading in the shallow end of the pool. The deep dive is the theory and practice book.
I also believe, if memory serves me right (the authors of the latter mention it, I did not proceed to count), that there is a 26 game overlap between the Lapshun (out of 82) and Theory and Practice (out of 95) books, though looking at a game twice from two different perspectives is not a bad thing. While the opening is now considered hogwash (Playing Bd3 in Bird's Opening that is and leaving the pawn on d2), how many times have you seen the Bird's opening game with the double Bishop sacrifice on h7 and then 2 moves later g7? I have seen it at least 3 times, all for a different purpose. One was an intro game from the 2006 Everyman book on Bird's opening while another was part of the Tactician's Handbook series - I think it was the 4th of 5, the others being Alekhine's Block, The Crosspin, Mitrofinov's Deflection, and the Steeple Chase. There were supposed to be two more, but never got published, and they then included those two plus the original 5 in a condensed version a decade or so later but with fragments instead of games. But the point is that seeing a game more than once isn't always a bad thing, especially from different people's perspectives.
Many have the misconception that mastering 1.b4 is a 30-minute exercise and that we are "lazy", but that just is not the case at all. It may not be as deep as the Najdorf, but it's not the Colle Koltanowski either!
Good luck with your endeavors!
I ordered Lapshun's "PLay b4!" and Konikowski's "b4. Theory and Practice" as well