Built-in shelving - first project, go/no go?

Hi folks, I've been planning to install built-in shelves for a while now around our chimney and could do with a more experienced eye before committing.

Any help much appreciated!

There's a few areas I think I need advice in:

1. Suitable fixings for an irregular wall
2. Suitable timber at a reasonable price with limited toolset
3. Finish

Fixings: I plan to affix a few lengths of 10mm square strip wood to the wall with raw plugs & timber screws, aligning the top surface of these strips may be a challenge. I'll then route out several pockets along the bottom edge of each shelf, then placing the pockets over the strips. Wood glue and panel pins will keep the shelves in place.

The shelves will be filled with books which I appreciate really add up - there are more to come than shown in the currently pictured bookshelf!

Timber: I've never purchased timber before other than some sheet plywood. I don't have access to a planer or table saw, so I believe I'll need to somewhat overpay for PAR timber close to final dimensions & cut down to length with a circular saw. I plan to order ~50mm longer than necessary as the walls are far from square.

The dimensions are 7 shelves of 25mm thick, 260mm wide, ~1650mm long. I also plan 3 more shelves on the opposite side, only 1050mm.

Pricing is leading me towards a pine (scandinavian redwood), am I setting myself up for disappointment? (Too soft, cheap finish?)

Am I missing any tricks? Just outside of a common dimension? Will 25mm be sufficient once 11mm is routed out for the pockets?

I have looked at window boards - these are an option, but are shallower than preferred at ~225mm max width.

timber2udirect and a few others are looking like £600.

Finish: I've been really impressed by the Fiddes Hard Wax Oil I used to restore my kitchen counter, I plan to get some of this with a light/antique satin finish.

I'm in the UK, hiring a van for this amount of timber could be an option, but I was planning on delivery. I can get access to most hand tools, but larger equipment isn't practical. Is the lack of a planer shooting