Lenovo B40-30 - 14 Celeron N2840 and debian 8 good match?

This is not a Debian forum.

Anyway, everything should be fine but Wifi and Bluetooth that have a high probability of not working. You cannot know for sure. The chipset (what matters for support) is never specified on new hardware. A same model can even sometimes have a chipset and sometimes another one.

Furthermore, the newer Lenovo laptops are known to (sometimes?) have hardware DRMs. That means you cannot switch the Wifi card to any card you want. The motherboard will just refuse the card. The remaining solution therefore is USB devices for Wifi and/or Bluetooth. Again, you usually cannot know the chipset of a new device. The only exceptions I am aware of are http://libre.thinkpenguin.com and http://tehnoetic.com that guarantee that all their hardware works with Linux-libre (hence with 100% free GNU/Linux systems). Both vendors sell Wifi adapter.

http://libre.thinkpenguin.com sells laptops too. You can there be certain that everything will work out of the box. You can even ask for the pre-installation any GNU/Linux system. On the contrary, if you buy the laptop you show us, you will enrich Microsoft even if you will never use the pre-installed operating system.

A last point: 2 GB of RAM is not much but is sufficient for mainstream usages (web browsing, e-mailing, chatting, playing medias, writing documents, etc.).

that laptop(as far as i know)
dose not run a free bios and may have DRM

also depending on what you need the pc for you i have these suggestions

all these computers can be run using entirely libre software

basic web browsing, programming, video, etc
the thinkpad x60(purchasable from around £30 on ebay)

my x60's specs
32-bit single core cpu 1.66ghz 2.25GB RAM(Expandable to 4GB)

3d games, web browsing, programming video etc(but faster than the x60)
the thinkpad x200/t400/t500/r400/t60

my x200's specs:
64-bit dual core cpu 2.25GHZ 2GB RAM(Expandable to 8GB)

SuperComputer:
http://libreboot.org/docs/hcl/kfsn4-dre.html

this motherboard can aparently support dual hex core cpu's
and 64gb ram